* Move MLIR to src/contrib/mlir

This patch enables LLVM optimizations at -O3 level.

We want to use ComputedKernel for any target to delimit sub-graphs to be
compiled and executed with MLIR.

* Create MLIR as cmake external project. Clone and build via ngraph cmake

* Moved code and enabled compilation. Need to clone and build MLIR/LLVM during cmake step, so find_package can work

* clone and build llvm/mlir during configuration. Compiles now. Needs more testing

* Force DEX only if MLIR is ON

* Remove extra cmake file. Style-apply

* Remove redundant files in cpu/mlir

* Update CODEOWNERS. Check for ninja and fail if not found

* Fixing post merge issues

* Implements a simple memory manager that just does malloc for now. Pointers are freed during cleanup.
* Enable JIT call-back to memory manager to allocate temps.
* Memory manager pointer is passed to the JIT'ed code upon invocation. That makes the code re-entrant from different threads in case the code is shared among identical sub-graphs that are executed in parallel.

The following test should work now:
NGRAPH_MLIR_DUMP_ALL=1 NGRAPH_MLIR=1 test/unit-test '--gtest_filter=CPU.dot2d'

* Link MLIR static libs to cpu backend

* Use LLVMConfig.cmake

* Initial commit. Link fails with undefined reference to typeinfo for mlir::Dialect

* Added AddOp

* initial compiler class

* Initialize module/function, and map tensors to arguments

* Code compiles. Moved MLIR building to correct DEX handler

* NGDialect code-gen working

* Use vector instead of sets for i/o tensors. Use functor in executor

* Misc fixes

* style-apply

* WIP: Adding support for dialect lowering.

* WIP: Lowered to affine. Crash on constant ops have side effects in Constant Folding

* Fixed missing whole package linkage.

* Removed fake instruction and update func type

*  Enable lowering to LLVM dialect and IR

* Made loop nest builder handle any rank

* Fixes per PR feedback. Major ones:
- Removed ngdialect namespace
- renamed dialect classes to start with NG prefixwq:w

* Add unreachable assert

* Add reading of LLVM options from an env var MLIR_LLVM_OPTIONS (#5)

* Link MLIR static libs to cpu backend

* Use LLVMConfig.cmake

* handle case where a node's output is connected multiple inputs of another node

* fix creation of the FunctionCall to have the correct outputs

* fix per review comment

* Cleanup how compile flags set and used by nGraph and external projects.
Set C++11 through CMake and pass it down to external projects.
Prefer CMake variables such as CMAKE_POSITION_INDEPENDENT_CODE and
CMAKE_CXX_STANDARD instead of explicitly setting compiler dependent
flags.
Create json compilation database for external projects.
CMAKE_CXX_FLAGS is used as common global options for nGraph and external
projects.
add_compile_options() is used for local options for current and sub
directories.
add_definitions() is used for setting definitions for current and sub
directories.
Note: Global options are not passed down to some external projects.
Note: mkl-dnn resets CMAKE_CXX_FLAGS internally.
Note: TBB and MLSL are not CMake based.
Noet: Eigen and json is header only library.

* Fix error.

* Fix error. (second attempt)

* Cleanup code.

* Allow check for undefined macro.

* Try to fix cldnn issue.

* Set type for CMake arguments.

* Pass C++ standard to protobuf.

* Pass C++ standard down to TBB.

* Change how Clang specific flags are handled.

* Fix error.

* Workaround for compile error on Baidu's PDPD docker.

* Fix windows build error.

* Initial implementation of implicit broadcasting for eltwise ops. Only Add supported

* Addressed PR feedback

* cleanup

* Rename Bcast to Broadcast

* Autobroadcasting support for rest of elementwise ops

* Serializer support for autobroadcast

* Added missing autob serialization for Minimum

* Added execution unit tests and more op types to implicit broadcast elimination

* Addressed PR feedback

* Fixes windows build issue

* RVO optimization per PR feedback

* serialize constant faster

* more speedup

* Draft of FakeQuantize operation along with UTs.

* Add FakeQuantize to implemented operators on IGPU.

* Get back FakeQuantize op case to switch.

* Fix compilation errors.

* Skip test for INTERPRETER backend and disable type_prop tests.

* Initial implementation covering the most basic case

* Cleanup of fake_quantize_with_clip UT

* Reformat the cpu unit tests manifest and unlock anothe fake quant UT

* Handle the clipping case by subtracting input_low from quantization input

* Clip the input data before quantization to avoid Selects

* UT manifest fix

* Obsolete comment removed

* Code formatting

* Broadcast input data for non-scalar in/out params

* Code formatting

* Enable the type prop tests for FakeQuantize

* Dequant the data without using the Dequantize op (fixes an edge case)

* Move reshape from utils to builder.

* Add aliases to functions in old place and describe changes.

* ShuffleChannels implementation

* Validation of ShuffleChannels params

* Implementation of ShuffleChannels decompose_op()

* Formatting adjustments

* Corrected implementation and validation of op params

* Basic test of ShuffleChannels

* Negative axis value test

* Default params for the ShuffleChannels op

* ShuffleChannels test with floats

* ShuffleChannels validation unit tests

* PR comments

* Compilation error fix

* PR feedback and cleanup

* Code formatting adjustment

* Negative axis value documentation

* Docs update (PR feedback)

* PR feedback: shape and axis validation

* Modify axis semantics on shuffle op

* Revert "PR feedback: shape and axis validation"

This reverts commit 21b708e710b91da2a7e37a69c0da1f31c7743b47.

Switch to clDNN version with conformance fix for 3 ONNX models (DenseNet-121, Inception-v2, ResNet-50) (#2982)

* Cleanup section

* Add updated illustrations for pattern_matcher and tensor_descriptor

* Add subsection link to be consistent

* update a few files to build on windows

* more fixes

* Switch some get_inputs uses to use the newer inputs

* Review comments

* Added CTCGreedyDecoder layer op

* Added comment on seq_len validation checks

* API defined

* add unit test for save/load with INTERPRETER

* Update per review comments

* fix compiler error

* Added accessor methods for layer op attributes

* style fixes and addressed PR feedback

* [ONNX] Unit test models for QLinearMatMul

* [ONNX] Extended types support for NgraphTestCase

* [ONNX] Move the value comparators to the NgraphTestCase class

* Add test cases

* Add shape checking

* disable GPU tests

* make private members protected in hybrid classes

* allow overriding the passes

* [Fused] LeakyRelu op

* Add LeakyRelu to serializer

* Add unit tests

* Fix merge branch 'master' into mkarzyns/fused_leaky_relu

* Change broadcasting rules to NumPy style

* Remove std:: and ngraph:: prefixes

* Rename CPU Runtime LeakyRelu to CPULeakyRelu

* Style apply

* Fix cpu_fusion.fuse_leaky_relu test

* Use eigen's tanh in the fused sigmoid multiply kernel (#2946)

* Merge branch 'master' into mkarzyns/fused_leaky_relu

* Add LeakyRelu to Intel GPU backend op list

* Add LeakyRelu to Intel GPU backend op list

* create tensor for the primary backend

* move private objects to protected

* Move zero padded conv fusions from CPUFusion to CoreFusion.

* Address PR feedback: move unit tests to core_fusion.

* Remove functions from cpu which were moved to core

* Fix a typo

* Remove unused function