* Implemented downgrade pass

* Using Pad:v1 in onnx_importer

* Downgrade transformation doc fixed

* Added downgrade pass for reduce_prod

* Using ReduceProd:v1 in onnx_importer

* Added ReduceProd:1 downgrade support

* Clang styles applied

* Downgrade pass added for all backends

* Added downgrade pass for reduce_prod

* Using ReduceProd:v1 in onnx_importer

* Added ReduceProd:1 downgrade support

* Clang styles applied

* Apply suggestions from code review

Changed pad_opset_pass to opset_downgrade
Co-Authored-By: Tomasz Socha <tomasz.socha@intel.com>

* Fix names

* Apply suggestions from code review

Removed redundant include, renamed tests
Co-Authored-By: Tomasz Socha <tomasz.socha@intel.com>

* Changed order of passes

* Changed way of op casting

* Changed order of passes

* Changed downgrade pass order of CPU backend

* Changed downgrade pass order of CPU backend

* styles applied

* [SPEC] Fixed NormalizeL2 (#3695)

* Fixed NormalizeL2

* style applied

* Fixed axes rank checking

* removed redundant comma

* Set keep_dims by function argument

* Improved error message

* Fixed casting method

* fix styles

* styles applied

* Fixed normalize tests

* unit tests names refactor
Co-Authored-By: Michał Karzyński <postrational@users.noreply.github.com>

* Disable not supported PlaidML tests

* Added missing EOF