Add multi-method support for ETRecord edge dialect programs

[larryliu0820]

Summary:
ETRecord previously only supported a single edge dialect program (defaulting to
the "forward" method). This change adds support for multiple methods like
vision_encoder, token_embedding, and text_decoder that are used in VLM exports.

The edge_dialect_program field can now be either a single ExportedProgram (for
backward compatibility) or a Dict[str, ExportedProgram] mapping method names to
their exported programs.

Key changes:

• Updated ETRecord to accept Dict[str, ExportedProgram] for edge_dialect_program
• Modified _process_edge_dialect_program to extract all methods from EdgeProgramManager
• Updated save/parse logic to handle multi-method format with backward compatibility
• New format uses paths like edge_dialect_exported_program/{method_name}

Authored with Claude Code.

Differential Revision: D92215098

[pytorch-bot]

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❌ 7 New Failures

As of commit de94c1c with merge base c0cef6c ():

NEW FAILURES - The following jobs have failed:

• Build documentation / build (buck2) / Build doc (gh)
  RuntimeError: Command docker exec -t af20cf7cdb992378b93224d84f4ada11ae818e0e6649cda10218515f03883b59 /exec failed with exit code 2
• Lint / lintrunner / linux-job (gh)
• pull / android / run-emulator (gh)
  The process '/usr/bin/sh' failed with exit code 1
• pull / unittest / linux / linux-job (gh)
  devtools/inspector/tests/inspector_utils_test.py::TestETRecord::test_executorch_export_etrecord_with_to_edge_flow_save_and_parse
• pull / unittest / macos / macos-job (gh)
  export/tests/test_target_recipes.py::TestTargetRecipes::test_mv3_model
• pull / unittest-arm-backend-with-no-deps (test_pytest_models_tosa) / linux-job (gh)
  RuntimeError: Command docker exec -t 5ae54d4ea4c640d9e6c3b2c6fbd812a6f5018f2d43c41cda7ad7f68d82255ba9 /exec failed with exit code 1
• pull / unittest-editable / linux / linux-job (gh)
  devtools/inspector/tests/inspector_utils_test.py::TestETRecord::test_executorch_export_etrecord_with_to_edge_flow_save_and_parse

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[meta-codesync]

@larryliu0820 has exported this pull request. If you are a Meta employee, you can view the originating Diff in D92215098.

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