Add hook-info field-shape conformance handlers

[wangyb-A]

Summary

Adds 5 conformance handlers (handlers/plugin/plugin_{invocation_info,operation_info,attempt_info,operation_change,context_info}_shape.ts) + template_plugin.yaml entries implementing plugin hook-info FIELD-SHAPE requirements 10-19..10-23 from aws/aws-durable-execution-conformance-tests#72 (land that PR first).

Each handler logs ONE single-line JSON record per hook event via process.stdout.write: a CANONICAL camelCase DUMP of that hook's own info parameter (undefined/null fields OMITTED — a missing key fails its assertion). GA note: experimental payload fields (execution input/result, operation result) are dumped when exposed but not asserted. The 10-19/10-23 handlers probe fields from the info objects at runtime and omit absent keys — the resulting reds are the intended signals.

Live validation (us-west-2): 20/23 — THREE DELIBERATE FAILURES (SDK parity gaps, tracked in #803)

• ❌ 10-19: InvocationEndInfo does not expose isFirstInvocation (Python/Java both do).
• ❌ 10-21: FAILED retryable attempt-end records lack startTimestamp/endTimestamp (AttemptEndInfo backfilled from the retry-pending operation, step-handler.ts ~457-465); the SUCCEEDED attempt-end passes.
• ❌ 10-23: attempt/user-function info has no isReplayingChildren (Python/Java expose it; JS models context functions via wrapChildContextFn).
• ✅ 10-20, 10-22, and the entire 10-1..10-18 regression.