Arm backend: Add support for StaticCache in TOSA+INT

[tom-arm]

• Create pass to decompose index_copy to index_put
• Enable INT tests for all targets except U55
• Adjust insert cast tests as the graph should delegate

Change-Id: I139728a78884ff1cbdc72568938f7b43f0b12279

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @Sebastian-Larsson @robell

[pytorch-bot]

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[Copilot]

Pull request overview

This PR extends the Arm backend’s INT/TOSA lowering path to support transformers.cache_utils.StaticCache by adjusting the pre-quantization graph transformations and enabling previously-xfailed INT tests (with U55 remaining xfailed due to SCATTER limitations).

Changes:

• Add a new transform-for-annotation decomposition pass to rewrite aten.index_copy{,_} into aten.index_put{,_} ahead of quantization/lowering.
• Update INT test expectations/config to align with the new decomposition behavior (including disabling fold_quantize where needed for StaticCache).
• Minor cleanup in RewriteIndexPutPass by removing an unused parameter from _expand_none_indices.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
backends/arm/test/passes/test_insert_int32_casts_after_int64_placeholders_pass.py	Updates INT test expectations to match index_copy→index_put decomposition and associated cast op presence.
backends/arm/test/modules/test_static_cache.py	Enables TOSA+INT/VGF quant StaticCache tests (removing prior xfails), sets fold_quantize=False, and refines U55 xfail reasoning.
backends/arm/_passes/rewrite_index_put_pass.py	Removes an unused parameter from _expand_none_indices and updates its call site.
backends/arm/_passes/insert_int32_casts_after_int64_placeholders.py	Drops index_copy{,_} from the “requires i64 input” callsite-cast map now that index_copy is decomposed earlier.
backends/arm/_passes/decompose_index_copy_pass.py	Introduces DecomposeIndexCopyPass to decompose aten.index_copy{,_} during transform-for-annotation.
backends/arm/_passes/arm_pass_manager.py	Wires DecomposeIndexCopyPass into the transform-for-annotation pipeline.
backends/arm/_passes/init.py	Exports DecomposeIndexCopyPass from the passes package.

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[Copilot]

Docstring grammar: "it's" is the contraction for "it is"; here it should be the possessive "its" ("...as well as its surrounding operators").

Suggested change

	"""Decomposes aten.index_copy into aten.index_put, as well as it's
	"""Decomposes aten.index_copy into aten.index_put, as well as its