[CI] Detect source breaking changes

[lorentey]

It would be nice to have a source compatibility check, but this project currently has the api-breakage-check "soundness" check disabled. Evaluate this check to see if it usable, and enable it if so.

Basic requirements:

1. We need to compare against a baseline that is configurable on a per-branch basis.
2. Automated source compatibility checks are extremely prone to false positives. Therefore, we need a reliable way to suppress any and all failures.

[FranzBusch]

It would be nice to have a source compatibility check, but this project currently has the api-breakage-check "soundness" check disabled. Evaluate this check to see if it usable, and enable it if so.

FWIW, we have this check enabled on all of our repos.

The reality is that this is actually an ABI breaking checker and not an API one but that's okay for us. We sometimes do get false-positives but we just admin merge over them once we come to the conclusion that this is in fact not an API breaking change.