Generate conformance-test SAM templates from handler metadata

## 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: https://github.com/aws/aws-durable-execution-sdk-java/pull/552#discussion_r3617917672

## 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_.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.

Start with PR #552 and the existing hand-maintained conformance-test SAM templates, then trace the Java handlers and their TestingMetadata.TestDescription mappings. Compare the local/CI conformance-test workflow with SAM validation/build and the step and wait suites. Done means deterministic templates, documented handler registration, successful suite runs, and CI protection against stale generated output.

Written by the indexing model from the issue text.