ci: replace Release Please with git-cliff releases

[leandrocp]

What changed

• Replace the repository-local Release Please workflow and configuration with the shared Elixir release workflow.
• Keep the existing RELEASE_PLEASE_TOKEN; no new token or GitHub App is required.
• Preserve the existing tag-triggered NIF and Hex publishing workflows.

Why

The shared workflow uses git-cliff to keep conventional categories and per-entry contributor credit while filtering Dependabot and other housekeeping changes. It maintains a release PR, then tags the release PR merge commit and creates the GitHub Release after merge.

Validation

• actionlint
• Shared formatter reproduced v0.2.7 with Bug Fixes and Documentation sections, contributor attribution, no dependency bumps, and no first-contribution section.
• Current v0.2.7..main history calculates no unnecessary release.