[clang] [analyzer] Give CStringChecker bug types proper descriptions (PR #219699)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

> I was thinking of what is the blast radius. How would this impact our users. It's probably for the better.

I strongly suspect that these bug type descriptions are ignored by practically all users, because they are never really interesting and they sometimes contain completely garbage values. (This was one of the most egregious examples.) 

https://github.com/llvm/llvm-project/pull/219699