Add RHEL support and include Linux distro in cache keys

[priyagupta108]

Description:

• Adds RHEL support for Python version resolution and installation.
• Includes the Linux distro (version + name) in the cache keys and aligns them across pip, pipenv, and poetry.

Impact:
One-time cache regeneration for Linux pipenv/poetry users on the first run. Windows and macOS keys are unchanged.

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.

[Copilot]

Pull request overview

This PR adds RHEL-aware Python release resolution and standardizes Linux cache keys by incorporating Linux distro name + version across pip/pipenv/poetry (while keeping Windows/macOS keys unchanged).

Changes:

• Add RHEL-specific manifest filtering during Python version resolution.
• Add a shared getLinuxInfoKeySegment() helper and use it to include Linux distro info in pip/pipenv/poetry cache keys.
• Make Linux distro detection more resilient by falling back from lsb_release to /etc/os-release.

Reviewed changes

Copilot reviewed 6 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/utils.ts	Adds fallback Linux distro detection via /etc/os-release when lsb_release fails.
src/install-python.ts	Adds RHEL detection and custom manifest matching for platform: rhel.
src/cache-distributions/cache-distributor.ts	Introduces shared Linux distro cache-key segment helper (incl. RHEL major-version logic).
src/cache-distributions/pip-cache.ts	Switches pip cache keys to use the shared Linux distro key segment helper.
src/cache-distributions/pipenv-cache.ts	Adds Linux distro segment to pipenv cache keys via shared helper.
src/cache-distributions/poetry-cache.ts	Adds Linux distro segment to poetry cache keys via shared helper.
dist/setup/index.js	Regenerated bundled output reflecting the source changes.

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