chore: Updated Dependabot config to group PRs and added workflow for scheduled auto-merge

[Rafi-Microsoft]

Purpose

• Introduced a scheduled GitHub Actions workflow to auto-approve and auto-merge Dependabot PRs targeting the dependabotchanges branch.
• Also optimized the dependabot.yml configuration to group dependency updates by ecosystem and path, significantly reducing PR noise.
• Enhanced rebase logic to handle merge conflicts using --strategy-option=theirs.
• Implemented multi-strategy auto-merge (merge, squash, rebase) with fallback handling.
• Improved overall script reliability and compatibility with repo-level merge restrictions.

Does this introduce a breaking change?

• Yes
• No

Golden Path Validation

• I have tested the primary workflows (the "golden path") to ensure they function correctly without errors.

Deployment Validation

• I have validated the deployment process successfully and all services are running as expected with this change.

What to Check

Verify that the following are valid

• ...

Other Information

[github-actions]

🎉 This PR is included in version 1.5.1 🎉

The release is available on GitHub release

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