Resolve "Run clan-format only for changed files in the CI"

Summary

Makes sure the clang-format check in the ci only runs for newly introduced changes. The newly introduced changes are compared to the default branch of the project or to the target branch of the merge request. However, with the way the whole ci is set up, the pipeline doesn't execute properly when you enable MRs to trigger this stage, so it essentially always picks the default branch. Should be good enough for now, but might be something to look at it in the future with how and when all the pipeline stages are triggered.

Requires manual tests in pre-production

NO

References

• Related to #98 (closed)

Closes #756 (closed)