Arm backend: Prevent illegal fusion in FuseEqualPlaceholdersPass

[YufengShi-dudu]

• Constant placeholders with same values but different data types, such as int32 and fp32, shouldn't be fused into a single placeholder. Otherwise, some operators will have operands with mismatched dtypes.
• Fix the bug by adding a dtype check to fuse only constants with matching types and same values.

Change-Id: Ia4668964f09010ac9416fc8c109549b7e989f724

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218

[pytorch-bot]

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❌ 3 New Failures, 1 Unrelated Failure

As of commit ce0ba95 with merge base 44d2643 ():

NEW FAILURES - The following jobs have failed:

• pull / test-llava-runner-linux / linux-job (gh)
  RuntimeError: Command docker exec -t d03c06e279133b7a1ebd4d3fedc4481a241ee22d30bbafb9e7c72dd336c339df /exec failed with exit code 139
• trunk / test-models-macos (llama3_2_vision_encoder, portable) / macos-job (gh)
  The process '/usr/bin/git' failed with exit code 128
• trunk / test-models-macos (w2l, xnnpack-quantization-delegation) / macos-job (gh)
  The process '/usr/bin/git' failed with exit code 128

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / test-moshi-linux / linux-job (gh) (trunk failure)
  test_exported_decoder_xnnpack

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