[clang] [llvm] [clang] NFC: Remove `{File, Directory}Entry::getName()` (PR #74910)

[Jan Svoboda via cfe-commits]

jansvoboda11 wrote:

Note: I'd like to merge this PR after we branch off for Clang 18 in January or February 2024. I had the patch lying around, so I figured I might as well create the PR.

https://github.com/llvm/llvm-project/pull/74910