Fix C++ warnings incorrectly classified as errors

[lapfelix]

C++ warnings with severity 1 were being classified as errors based solely on categoryIdent (e.g. "Parse Issue"), ignoring the severity field. Now uses severity to distinguish warnings (severity 1) from errors (severity 2+) for all ambiguous categories.

Added a test to cover this case.

To cover these warnings (which Xcode considered warnings in my build):

[lapfelix]

Oh woops I forgot I had this PR open and kept committing more fixes I needed to my master branch

[AvdLee]

@lapfelix I'm ready to merge this in, but the checks are failing. Would you see a moment to check and solve accordingly? 🙏