ONNX Loop (#2847)

ONNX Loop (#2847)

* Loop op ngraph implementation, update IE IR Reader and ngraph to cnn converter

* refactoring SubGraphOp class

* type prop unit tests

* ngraph code style

* update comment

* single layer tests for Loop operation

* fix file name

* Add SpecialBodyPorts attribute in Loop op, update single layer tests

* first debug version

* more tests

* missing test file

* removed not needed shapes from test data

* move test data to new folder

* shape infer tests

* Added execution tests

* add several new tests cases, strict checks in Loop impl, temporary disable single layer tests

* ngraph codestyle, refactoring, clone_new_args test

* resolve review remarks

* fix build

* fix tests

* more execution tests

* add a new constructor of Loop op, resolve review remarks

* execution tests

* synchro with current version

* handle scalars and more tests

* scalar test enabled

* loop reference impl

* bug fixes in tests, onnx importer part and in the ref implementation of the Loop op

* applied remarks

* handle unsupported cases

* rewrite unit tests

* update INTERPRETER manifest

* is_termination_condition_always_true simplification

* [TEST] update python models tests

* review remarks

* added xfail to tiny_yolov3

* missing model test

* revert test data

* fixed numbers of failing tests

* fixed failed test description

* fix test message

* fix xfail test

* zoo models tests clean-up

* missing comma

Co-authored-by: Ivan Tikhonov <ivan.tikhonov@intel.com>