[libc++][nfc] Improve error diagnostics.

The error message for disabled filesystem and locale support is now done
in the same fashion as ranges and format in D106763.

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D106935

GitOrigin-RevId: 4e65688571221565cf1a5c1e4bb58ee2ab7c9c83
2 files changed