Document provisioning metadata examples

[justusschock]

Summary

• document Job/MMT/Studio provisioning metadata introduced by the base branch
• add optional --placement-group-id usage to Job and MMT examples
• print resource IDs, private IPs, placement groups, and ranked MMT members in examples
• add a focused regression test that keeps the examples wired to the public metadata surface

Stack

Stacked on top of #19 (justus/monarch-provisioning-metadata).

Verification

• uv run --with-requirements python/tests/requirements.txt --with ./python pytest python/tests/core/test_provisioning_examples.py -q
• uvx pre-commit run ruff --files python/examples/jobs.py python/examples/mmts.py python/examples/studios.py python/tests/core/test_provisioning_examples.py
• uvx pre-commit run ruff-format --files python/examples/jobs.py python/examples/mmts.py python/examples/studios.py python/tests/core/test_provisioning_examples.py
• uvx pre-commit run mdformat --files python/examples/jobs.rst python/examples/mmts.rst python/examples/studios.rst