Make Flax pt-flax equivalence test more aggressive (#15841)
* Make test_equivalence_pt_to_flax more aggressive
* Make test_equivalence_flax_to_pt more aggressive
* don't use to_tuple
* clean-up
* fix missing test cases + testing on GPU
* fix conversion
* fix `ValueError: assignment destination is read-only`
* Add type checking
* commit to revert later
* Fix
* fix
* fix device
* better naming
* clean-up
Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>