[clangd][nfc] cleanup of remaining clang-tidy findings

There were some left-overs (or new things) from the previous patches.

This will get us down to 0 open findings except:
clang-tidy is complaining in some files about
`warning: #includes are not sorted properly [llvm-include-order]`
however, clang-format does revert these changes.
It looks like clang-tidy and clang-format disagree there.

Not sure how we can fix that...

Reviewed By: sammccall

Differential Revision: https://reviews.llvm.org/D118698