TI and Sequences related transformations: transition from cnn to ngraph versions (#2927)
* sequences to ti transformations, support for seq_lengths input, update reference implemetations, add new tests
* fix python api, update sequences to ti transformation
* transition from cnn to ngraph transformations for cpu, gpu, vpu plugins
* fix convert_ti_to_sequence transformation
* fix naming issue in unroll transformation
* test pure TensorIterator in vpu plugin
* fix sequences to ti transformation
* Update sequences to TI transformation: fix reverse sequence support
* update single layer tests, fix TI reference impl, fix Sequences to TI transformations
* ngraph code style
* fix build
* fix ngraph python api
* resolver review comments, refactoring
* revert vpu changes
* disable/fix tests
* refactoring
* Resolve review remarks
* optimization of LSTMSeq -> LSTMSeq IE: remove unnecessary Transpose ops
* Refactoring of transformation pipeline in cpu and gpu plugins, align GRU/RNN -> GRU/RNN IE with LSTM -> LSTM IE
* update TensorIterator tests, refactoring
* fix typo
* Fix unit tests, delete unnecessary callbacks
* Refactoring: delete commented code
* Add FullyConnected to skipConstInfer list for legacy ConstFolding
* disable legacy cnn unit tests
* delete xfail
* fix for backward compatibility with opset1::LSTMCell
* delete xfail
* fix build, remove Reshape layer from skipConstInfer list
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