chore(changelog-check): add action-sha input for correct repository checkout

[cryptodev-2s]

Description

This PR adds an action-sha input to the changelog check workflow to ensure we're using the correct version of the github-tools repository. This is necessary because:

1. When a workflow is called using a specific SHA (e.g., @91e349d177db2c569e03c7aa69d2acb404b62f75), we need to use that exact same SHA when checking out the repository
2. Previous attempts using github.action_ref, github.sha, or other GitHub context variables didn't work because:
   • github.action_ref includes the full ref path (e.g., +refs/heads/v4*:refs/remotes/origin/v4*)
   • github.sha refers to the current workflow run's SHA
   • Other context variables don't reliably provide the correct SHA

Long-term Plan

This is a short-term fix. In the future, we plan to:

1. Move the workflow to a separate repository
2. Implement proper versioning for the tools
3. Use GitHub Actions' built-in versioning system
4. Remove the need for manual SHA management

Changes

• Added new required input action-sha to the workflow
• Updated the checkout step to use ${{ inputs.action-sha }}
• This ensures we're using the exact same version that was specified in the workflow call

Testing

1. This change is being tested in MetaMask/core#5693 where we're updating the changelog check workflow to use the new action-sha input.

2. Test with a workflow call using a specific SHA:

   uses: MetaMask/github-tools/.github/workflows/changelog-check.yml@91e349d177db2c569e03c7aa69d2acb404b62f75
   with:
     action-sha: 91e349d177db2c569e03c7aa69d2acb404b62f75
     # ... other inputs ...

   • Verify that the workflow successfully checks out the correct SHA

3. Verify that the checkout works correctly and matches the version used in the workflow call

[rekmarks]

LGTM.