Support mutable operations (set, swap, addupdate) on ReshapeTransform and BitcastTransform views during state discharge.

[copybara-service]

Support mutable operations (set, swap, addupdate) on ReshapeTransform and BitcastTransform views during state discharge.

Previously, ReshapeTransform and BitcastTransform were read-only during state discharge (ref_get). Attempting to mutate them via ref_set, ref_swap, or ref_addupdate failed with NotImplementedError because the write-back loop in transform_swap_array only handled NDIndexer. Additionally, the forward pass in transform_swap_array did not update the transformed value accumulator, which caused swap to return an un-transformed value.

This change:

• Implements reverse transformations (.reshape(...) and bitcast(...)) during the write-back phase in transform_swap_array.
• Rebinds new_val during the forward pass in transform_swap_array so swap returns the correctly transformed previous value.
• Adds support for ReshapeTransform in _addupdate_discharge and explicitly disallows BitcastTransform on addupdate.
• Adds unit tests in state_test.py covering set, swap, sliced view mutations, and addupdate on reshaped and bitcast views.
• Adds test coverage in pallas_test.py verifying behavior under Pallas interpret mode and explicit NotImplementedError under Triton.