feat(sdk): monorepo repository to add new otel plugin package

[SilanHe]

Issue #, if available:

Description of changes:

Monorepo Restructure

The repo was converted from a single-package layout to a monorepo with a packages/ directory:

• Core SDK moved from the repo root (src/, tests/, examples/, pyproject.toml) into packages/aws-durable-execution-sdk-python/
• All source, tests, and examples were relocated (no content changes, just path moves)

New Package: OpenTelemetry Instrumentation

A new package was added at packages/aws-durable-execution-sdk-python-otel/ (v0.1.0):

File	Purpose
pyproject.toml	Hatch-based build config; depends on core SDK ≥1.5.0, opentelemetry-api ≥1.20.0, opentelemetry-sdk ≥1.20.0
__init__.py	Placeholder module (exports __version__ only, no instrumentation logic yet)
README.md	Documents the intended API (instrument_durable_execution()) and features
tests/	Empty test directory
py.typed	PEP 561 marker

CI & Workflow Updates

• ci.yml — Loops over all packages/*/ directories for format checks, type checking, tests, and builds
• ci-checks.sh — Iterates over a PACKAGES array instead of running checks at the repo root
• pypi-publish.yml — Uses a matrix strategy to build and publish each package independently; per-package artifact names
• sync-package.yml — Deleted (no longer needed)
• deploy-examples.yml / integration-tests.yml — Minor path adjustments

Documentation

File	Change
CONTRIBUTING.md	Updated with monorepo structure overview; instructions to cd into package dirs before running hatch
RELEASING.md (new)	Release process: per-package versioning, tagging convention (sdk-vX.Y.Z, otel-vX.Y.Z), PyPI publishing flow, release notes format, pre-publish checklist
Core SDK README.md (new)	Package-level README inside the moved package directory

Misc

• .gitignore — Relaxed example build/zip patterns from root-anchored to relative (works with nested layout)

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[SilanHe]

I haven't actually tested this one but it looks quite reasonable. I had to work a little more closely with AI on this one.