[libc++] Use addressof in vector.

This addresses the usage of `operator&` in `<vector>`.

I now added tests for the current offending cases. I wonder whether it
would be better to add one addressof test per directory and test all
possible violations. Also to guard against possible future errors?

(Note there are still more headers with the same issue.)

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D111961