Generate conformance-test SAM templates from handler metadata

[zhongkechen]

Summary

PR #552 adds hand-maintained SAM templates for the Java conformance test suites. Each handler requires a largely repetitive Lambda resource plus a TestingMetadata.TestDescription mapping to conformance requirement IDs. As the number of handlers and suites grows, maintaining these mappings in both Java code and SAM YAML will be error-prone.

Add a script or build step that generates the conformance-test SAM templates from handler metadata.

Review context: #552 (comment)

Requirements

• Define one source of truth for the mapping between each Java handler and its conformance requirement IDs. This could be a Java annotation, a small manifest, or another explicit convention.
• Generate template_<suite>.yaml files deterministically for all conformance suites.
• Preserve the shared SAM configuration and each function's TestingMetadata.TestDescription values.
• Integrate generation into the local/CI conformance-test workflow so templates cannot silently drift from handlers or metadata.
• Document how to add a handler and its requirement mapping to an existing or new suite.

Acceptance criteria

• Adding or removing a conformance handler requires no manual duplication of its Lambda resource in a SAM template.
• Generated templates pass SAM validation/build and run the existing step and wait conformance suites successfully.
• Generation is stable: running it twice without source changes produces no diff.
• CI fails when checked-in generated templates are stale, or generates templates before they are consumed if they are not checked in.