[clang-tools-extra] [clang-apply-replacements] Deduplicate Implementation of `collectReplacementsFromDirectory` (NFC) (PR #78630)

[Daniil Dudkin via cfe-commits]

unterumarmung wrote:

I honestly don't who should review/approve this, but hopefully the change is not complicated.

https://github.com/llvm/llvm-project/pull/78630