ci: publish durable execution lambda layer (EXPERIMENTAL)

[zhongkechen]

Summary

• add a GitHub workflow to build and publish public Lambda layer versions for the SDK + OTel plugin
• add a repo script for building runtime/architecture-specific layer zips
• document manual and release-driven layer publishing

Testing

• hatch fmt --check .github/scripts packages/aws-durable-execution-sdk-python-otel
• hatch run test:all .github/scripts/tests/test_build_lambda_layer.py .github/scripts/tests/test_parse_sdk_branch.py packages/aws-durable-execution-sdk-python-otel/tests
• hatch run types:check
• hatch build (OTel package)
• python3 .github/scripts/check_dist_legal_files.py packages/aws-durable-execution-sdk-python-otel
• workflow YAML parse check

[yaythomas]

this just for testing?

rather than triggering on release?

[yaythomas]

it doesn't really matter all that much given there's only 1 job in here currently, but generally the pattern we follow is read at the top level and write only on the jobs that need it.