CxxUtils: add option to enable pedantic gccchecker plugin settings
Add CHECKERGCCPLUGINS_PEDANTIC CMake option to enable more strict
gcc checker plugin settings.
Currently the only difference is that the thread-checker is enabled for all files in the repository. We could then add a separate nightly build (requested in ATLINFR-4570) that runs with this option to make the full list of checker warnings available to a larger community. I imagine it could also be useful to validate other new features of the checker in the future.