Add CSEPass to the default edge compilation pipeline (#19849)

[billmguo]

Summary:

CSEPass (Common Subexpression Elimination) was previously only used by specific backends (MLX, Cadence) and export scripts. This change adds it to base_post_op_replace_passes in the default to_edge / to_edge_transform_and_lower pipeline so all backends benefit from CSE automatically.

The pass is placed before dead_code_elimination_pass so any dead nodes CSE creates get cleaned up, and before DebugHandleGeneratorPass so debug handles are assigned to the final deduplicated graph.

CSE can merge structurally-identical nodes across different source partitions, which caused ConvertToLinearPass in XNNPACK to see extra output nodes in a partition. This is fixed by filtering outputs to only those reachable from the mm/addmm node within the partition.

The test_dim_order_revert_pass test is updated to expect 2 _to_copy ops (instead of 4) after to_edge, since CSE deduplicates the two identical branches.

Reviewed By: mohankumarkumar

Differential Revision: D106584552

[pytorch-bot]

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❌ 3 New Failures, 4 Unrelated Failures

As of commit cc4c35e with merge base 84c0484 ():

NEW FAILURES - The following jobs have failed:

• pull / test-arm-backend-no-driver (test_pytest_ops_tosa) / linux-job (gh)
  RuntimeError: Command docker exec -t 1d4c46558637c95ce5e2eb9ad1c4aadaf8ddbf3ed13c4b1662f641cec3e845a0 /exec failed with exit code 1
• trunk / test-arm-backend-ethos-u (test_pytest_ops_ethos_u85) / linux-job (gh)
  RuntimeError: Command docker exec -t 2b51608f9e98b817e01dd82baedfbe82479e66d375ccb90b22c1f602cc5c5d52 /exec failed with exit code 1
• trunk / test-arm-backend-vkml (test_pytest_ops_vkml) / linux-job (gh)
  RuntimeError: Command docker exec -t 37ff1f47c1c086e114165bb955fd73cce27b8e789107a4338b5da69a955306e6 /exec failed with exit code 1

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

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

• pull / unittest / macos / macos-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / unittest-editable / macos / macos-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• trunk / test-arm-backend-ethos-u (test_smaller_stories_llama) / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• trunk / unittest-release / macos / macos-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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