add the operations needed for electra model (#82856)
- Add equality constraints and dimension constraints
- Bypass an error for getitem(not relavant to control-flow but needs to be revisited later)
- Add test-cases.
- Full test-case for model can be seen here https://github.com/migeed-z/transformers/pull/3/files
Pull Request resolved: https://github.com/pytorch/pytorch/pull/82856
Approved by: https://github.com/jansel
