clang-tidy fixes

I still find it somewhat difficult to look at the git diff changes in !7 (closed), so I cherry-picked and adjusted the clang-tidy fixes to this branch in small commits. I also enabled all clang-tidy flags again and disabled from there. For two checks (definitions in std namespace and reinterpret cast) I used inline exceptions instead of silencing it, since I find them good checks in general. For two checks with low priority (possible exception in main, llvm-include-order since no case insensitive sorting) I disabled the werror flag (I think we should fix the first and disable the second in a clang-format MR).