[Infra] Update release process

[martincostello]

Changes

• Explicitly state which permissions are required when obtaining a GitHub App token.
• Add the appropriate permission to allow invoking a GitHub Actions workflow.

Contributes to #6556.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.84%. Comparing base (c724f4b) to head (9fa205c).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7034      +/-   ##
==========================================
- Coverage   88.85%   88.84%   -0.01%     
==========================================
  Files         271      271              
  Lines       12970    12970              
==========================================
- Hits        11524    11523       -1     
- Misses       1446     1447       +1     

Flag	Coverage Δ
unittests-Project-Experimental	88.71% <ø> (-0.07%)	⬇️
unittests-Project-Stable	88.73% <ø> (-0.04%)	⬇️
unittests-Solution	88.80% <ø> (-0.03%)	⬇️
unittests-UnstableCoreLibraries-Experimental	41.27% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.
see 3 files with indirect coverage changes

[Copilot]

Pull request overview

This PR updates the release/publishing GitHub Actions workflows to explicitly scope the permissions granted to the generated GitHub App tokens, and adds the required actions: write capability for dispatching workflows in the opentelemetry-dotnet-contrib repository.

Changes:

• Scope GitHub App token permissions explicitly (contents / pull-requests) in multiple workflows.
• Grant actions: write to the GitHub App token used to invoke a remote workflow dispatch.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
.github/workflows/publish-packages-1.0.yml	Scopes the GitHub App token to explicit contents/PR permissions for post-build release drafting and PR notifications.
.github/workflows/prepare-release.yml	Scopes GitHub App tokens across multiple prepare-release jobs to explicit contents/PR permissions.
.github/workflows/post-release.yml	Adds explicit permissions to GitHub App tokens, including actions: write for invoking a remote workflow.

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[martincostello]

As discussed in https://github.com/open-telemetry/admin/issues/615, for now this drops the automatic workflow generation and instead changes the release process to be manual.

Will look to add some automation to opentelemetry-dotnet-contrib to do a scheduled workflow and compute what tags should have a PR created. If that gets implemented, then I can do a follow-up PR to adjust the documentation.

[martincostello]

3.1.0 of the action made app-id deprecated in favour of client-id - spotted via a squiggle locally when I was updating the files in VS Code.