ci: use git diff to add `M-database-changes` label for pr that contains migrations and schema changes

[ShankarSinghC]

Type of Change

• [ ] Bugfix
• [ ] New feature
• [ ] Enhancement
• [ ] Refactoring
• [ ] Dependency updates
• [ ] Documentation
• [x] CI/CD

Description

This ps uses git diff to add M-database-changes label for pr that contains migrations and schema changes.

Additional Changes

• [ ] This PR modifies the API contract
• [ ] This PR modifies the database schema
• [ ] This PR modifies application configuration/environment variables

Motivation and Context

How did you test it?

We can see that M-database-changes was added for on of the below commits which contained migration changes.

Checklist

• [x] I formatted the code cargo +nightly fmt --all
• [x] I addressed lints thrown by cargo clippy
• [x] I reviewed the submitted code
• [ ] I added unit tests for my changes where possible