validate_mr: Create keyword in MR title to allow skipping body validation
General MR
Summary
Note: this MR merges into the bigbang pipeline check (that in turn merges into the package pipeline check).
Allows an MR creator to include the phrase SKIP SUMMARY CHECK in the MR title to avoid running the validate_mr pipeline that checks for upgrade notices.
Relevant logs/screenshots
To test this I disabled the clean upgrade (to speed up the pipelines) and briefly changed the conditional to check the commit message instead of the MR title, and then ran two tests using the pipeline validation process:
The one with SKIP SUMMARY CHECK skipped the validation pipeline and only executed 2 steps, the other executed all three.