feat: Added Endpoint Integration for CMA Python SDK

Fix/backmerge 16 06 2026

…ld time.

- Add `contentstack_management/region_refresh.py` exposing a `refresh_regions()`
  function that downloads the latest regions manifest from the Contentstack CDN
  and overwrites the bundled `data/regions.json`.
- Export `refresh_regions` at the package level so CI pipelines and tooling can
  call it programmatically (`from contentstack_management import refresh_regions`).
- Hook `setup.py` with a custom `BuildPyWithRegions` command so `regions.json`
  is refreshed automatically on every `python setup.py build` / `pip install`,
  keeping the bundled region data current without a manual step.