* The stack operator support for a engine:
1) Added the package of stack tests
2) Added stack fused operator
3) Modified cmake file to support stack operator

* 1) Support for a v0 version

* Stack.cpp file is modified
1) Removed unused function

* The stack.cpp file is modified:
1) Empty line was removed: [line: 72]

* Modification of test/backend/fused_op.in.cpp file
1) [line 1340], fall back to the previous version of comment

* Code refactoring:
1) Comment message is different, adjusted to get much more details about stack operator
2) Seralize.cpp file is adjusted to work with stack operator

* Added:
1)generated_adjoints has not implemented yet.
2)int64_t -> size_t

* The variable stored negative value was removed from the code

* Source files: code-format check

* Added included

* fix error

* set output type