CI+CMake: Enable Clang plugins for Serenity Clang builds

[ADKaster]

:partying_face:

As a note, the Lambda capture one is very noisy.

And the warnings from these plugins don't seem to respect -Werror which is... good(?)

[mattco98]

As a note, the Lambda capture one is very noisy.

Yeah I'm going to invert this so that functions that do escape are annotated. After that, I can make the plugins emit errors instead of just warnings. Not sure how useful running this on CI will be until that happens, but I suppose it can't hurt (assuming there are no performance impacts, which I haven't tested!)

[ADKaster]

I'll drop the CI commit until we can have the warnings enforced :)