feat: add Update Changelogs workflow with auto-changelog v6 --checkDeps

[cryptodev-2s]

Explanation

Adds an Update Changelogs workflow that uses @metamask/auto-changelog v6's --checkDeps --fix feature to automatically validate and fix missing dependency bump changelog entries.

Triggers:

• Automatic: When a release PR (release/* branch) is opened targeting main
• On-demand: Comment @metamaskbot update-changelogs on any non-fork PR

What it does:

1. Detects and skips fork PRs (security)
2. Checks out the PR head branch
3. Runs changelog:validate --checkDeps --fix --currentPr <PR#> across all packages
4. Commits and pushes any CHANGELOG.md fixes back to the PR branch
5. Comments on the PR with the result

Security:

• Fork PRs are blocked via isCrossRepository check
• All dynamic values use environment variables (no ${{ }} in run: blocks)
• SHA-based checkout with branch name switch for release branch detection
• 30-minute job timeout

References

N/A

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

---

Note

Medium Risk
Adds a GitHub Actions workflow that checks out PR branches and can commit/push changes to **/CHANGELOG.md, so misconfiguration could cause unintended automated commits despite fork checks and scoped triggers.

Overview
Introduces a new GitHub Actions workflow (.github/workflows/update-changelogs.yml) that can be triggered on release PR creation (release/* into main) or via an @metamaskbot update-changelogs PR comment to validate and auto-fix dependency bump changelog entries.

The job skips fork PRs, checks out the PR head SHA, runs yarn ... changelog:validate --checkDeps --fix --currentPr, then commits and pushes any CHANGELOG.md updates back to the PR branch and comments the outcome on the PR.

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