[CRCR] Add failed-tests-detail input to callback action and ingest path

[subinz1]

Summary

Adds support for per-test failure details in the CRCR pipeline, addressing the ingest portion of #8545.

• Callback action: new failed-tests-detail input accepting a JSON array of {name, classname, message, duration} objects
• report_callback.py: passes the new field as workflow.failed_tests_detail, capped at 50 entries
• crcrUtils.ts: extracts and persists as failed_tests_json in DynamoDB/ClickHouse, with message truncation at 500 chars

Size caps

Cap	Value	Rationale
Max entries	50	Prevents DynamoDB 400KB item overflow
Max message length	500 chars	Enough for assertion line, not full stacktrace

Usage (downstream workflow)

- uses: pytorch/test-infra/.github/actions/cross-repo-ci-relay-callback@main
  with:
    status: completed
    conclusion: failure
    failed-tests-detail: |
      [
        {"name": "test_foo", "classname": "TestBar", "message": "AssertionError: expected True"},
        {"name": "test_baz", "classname": "TestQux", "message": "RuntimeError: CUDA OOM"}
      ]

Test plan

• Verify callback action passes the field through to the relay
• Verify extractDynamoRecord persists failed_tests_json when present
• Verify size caps work (>50 entries truncated, long messages clipped)
• Verify missing/empty failed-tests-detail doesn't break existing flow

Closes the ingest path portion of #8545. UI drill-down will follow in a separate PR.

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[subinz1]

Addresses #8545 (ingest path portion).