Move PropagateCastOps metadata to compile time

[GopalakrishnanN]

Description

• Replace the two function-local InlinedHashMap tables used by PropagateCastOps with one constexpr operator argument descriptor table.
• Store explicit active input/output counts so the compact fixed-capacity arrays preserve the existing policy exactly.
• Validate sorted unique operator names, non-empty argument sets, in-range counts, non-negative indices, and duplicate indices with consteval checks.
• Add an independent exhaustive compile-time truth table for all seven operators, plus a runtime lookup test.

Motivation and Context

The relevant input/output policy is fixed program metadata, but it was represented by two separately initialized runtime hash maps. Consolidating it removes duplicate operator keys, makes policy drift a compile-time failure, and avoids runtime hash-table initialization and allocation.

Unknown operators still use the existing fallback where every input/output is relevant.

Measurement

Windows RelWithDebInfo, MSVC 19.51, touched-file rebuild of propagate_cast_ops.cc:

Artifact	Before	After	Delta
propagate_cast_ops.obj	7,196,523 B	6,353,108 B	-843,415 B
onnxruntime_optimizer.lib	255,830,720 B	254,651,324 B	-1,179,396 B

The single baseline rebuild was 10.83 s; post-change samples were 13.45 s, 12.37 s, and 12.06 s. Build timing is noisy and this PR does not claim a compile-time improvement.

Testing

• cmake --build build/Windows/RelWithDebInfo --config RelWithDebInfo --target onnxruntime_test_all --parallel 8
• onnxruntime_test_all.exe --gtest_filter=PropagateCastOpsMetadataTest.*:GraphTransformationTests.PropagateCastOpsTests* from the test output directory: 2 tests from 2 suites passed.
• lintrunner -a on all three changed files: no lint issues.

[Copilot]

Pull request overview

This PR moves PropagateCastOps operator argument metadata from runtime-initialized hash maps to a single compile-time (constexpr) descriptor table, enforcing metadata consistency via compile-time validation and adding targeted tests to prevent policy drift.

Changes:

• Replaced runtime InlinedHashMap metadata tables in PropagateCastOps with a constexpr kRelevantOpArgs table and a FindRelevantOpArgs lookup helper.
• Added consteval/static_assert validation of metadata invariants (sorted unique op names, valid non-empty index sets, no duplicate indices).
• Added a new unit test that performs an exhaustive compile-time truth-table check plus a small runtime lookup test.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
onnxruntime/core/optimizer/propagate_cast_ops.cc	Switches relevance checks to use the new compile-time metadata lookup.
onnxruntime/core/optimizer/propagate_cast_ops_metadata.h	Introduces the compile-time metadata table, validation, and lookup helper for relevant input/output indices.
onnxruntime/test/optimizer/propagate_cast_ops_metadata_test.cc	Adds compile-time and runtime tests to lock in the expected metadata behavior.