* - WIP fusion pattern for softmax + cross entropy

* fix compiler error

*  make summation axis integer for the fusion pattern

* - Fusion pattern for sigmoid cross entropy bprop

* WIP callback implementation for fused sigmod+crossentropy fprop

* - implemented fprop softmax+crossentropy as single layer for numerical
stabilization
- added broadcasting nodes to fix elementwise assertions

* Added unit test case for functionality test

* Move the softmax + crossentropy fusion pass to core

* i) style fix ii)added missing header

* - Added new Fused Op for Softmax + CrossEntropy
- moved the decomposition to the Softmax + CrossEntropy FusedOp

* - Add SoftmaxCrossEntropy for fused tablegen
- Add serializer support for SoftmaxCrossEntropy
- fix documentation

* Added missing json file for unit test case

* Addressed PR comment

* Addressed PR comments

* - Fix fusion string

* - Style fix

* - Added Bprop for Softmax + crossEntropy

* - added SoftmaxCrossEntropy support when soft_lable is provided
- serailizer and deserializer support for SoftmaxCrossEntropyBprop

* - Added support in decompose_op for SM+CE bprop when ignore_mask is specified

* Updated Doc strinng

* - unit test case for SoftmaxCrossEntropy backprop with soft lables
- fixed decompose_op bug in bprop

* - if soft_label=true, capture pattern only if the labels dont have one
hot encoding

* - SoftmaxCrossEntropyBprop Support if ignore_index is specified

* add serialized files for unit test

* - fix softmax + CE pattern bug
- fix softmax + CE decompose_op() bug

* - change reduction_axes to int64_t type in fprop and bprop ctor

* - add soft_labels and ignore_index attribute to SM+CE fprop ctor

* - addition asserts in unit test to ensure SM + CE fprop and bprop fusion is successful

* - move reduction_axis computation to decompose_op from ctor to relax on
dynamic shapes

* Addressd PR Comments

* - suppprt for SM+CE for ignore_index and softmax=false

* - test case for SM+CE fprop with ignore_mask, soft_labels=false
- fix bug in decompose_op

* - refactor unit test case

* - fix PDPD unit test

* broadcast delta if shape mismatches

* -fix bdcast issue in decompose_op