[TENSORFLOW]StatefulPartitionedCall/PartitionedCall Ops support added (#5617)

[TENSORFLOW]StatefulPartitionedCall/PartitionedCall Ops support added  (#5617)

* Implemented functionInvocation Unit Test for StatefulPartitionedCall operator(working) and initial changes for placeholder(not working as of now)

* Placeholder exercises with tvm

* placeholder interim

* SPOP Test cases structure

* New test cases for spop

* miscellaneous test cases for spop

* Placeholder samples..working with shapes explicitly passed

* Variables test case. Works with the same fix of shape_dict

* SPOP Positive test cases first iteration

* support output tensors as function args, multiple functions

* Corrected Indentation

* filewritter is only for debug purpose

* support variables in function args

* First working iteration of positive spop test cases

* Removed commented code, simplified code

* Code Reorganization- First working iteration of positive spop test cases

* corrected variable name after refactor

* Code Reorganization- First working iteration of positive spop test cases

* move code inside mapped operator function

* Removed extra line

* support variables in function args

* Removed commented code, simplified code

* move code inside mapped operator function

* Code Reorganization- First working iteration of positive spop test cases

# Conflicts:
#	tests/python/frontend/tensorflow/test_forward.py

* Code Reorganization- First working iteration of positive spop test cases

* Function invocation more test cases

* Simplified & Merged different Function Invocation Test cases

* support invocation of nested callables

no need to explicitly handle paratitioned and
statefulPartitioned condition in convert_operator function

* Simplified and Uniform testcases

* support invocation of nested callables

no need to explicitly handle paratitioned and
statefulPartitioned condition in convert_operator function

* Simplified and Uniform testcases

* removed duplicate and renamed testcase

* Negative scenario added for testing operator statefulness. Only Exception to stateful operators are Partitioned & StatefulPartitionedOp which have capability to execute even stateless operators within them

* Miscellaneous reorganization changes for spop scenarios

* Miscellaneous reorganization changes for spop scenarios

* Corrected import of tensorflow modules safely using try except and other code reorganization

* Negative scenario for resource variables handled

* Documentation update for code

* SPOP change in function handling

* handle nested subgraph

* refactor

* get op def compatible with tf 1x & 2x

* Fixed liniting issues

* added doctsring and few nits

* Merged changes for positive test cases and negative test cases

* Moved StatefulPartitionedCall test case to the end of the TC list

* Fixed some typos and semantics

* dmlc-core

* dmlc-core

* fixes

* Addressing Review comments in the PR for SPOP support

* Fixed pylint errors

* Corrected tensorflow import syntax

* Placed the op_def_registry module import outside of for loop

* Removed new stateful operators list and combined these operators with missing operators to display as single list. Also removed throwing seperate exception for stateful ops

Co-authored-by: Prashant Sail <psail4444@gmail.com>
Co-authored-by: maheshambule <mahesh_ambule@persistent.com>