Layer norm fusion deepspeed stage3 changes (#17614)
### Description
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Layer norm fusion changes required for deepspeed stage 3, also includes
test case.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
It helps fusing layer norm for Deepspeed Stage 3. Added a test case
scenario which ensures that the fusion is working properly for the
scenario.
