Revert "[clang-tidy] Confusable identifiers detection"

This reverts commit b94db7ed.
See comments on https://reviews.llvm.org/D112916:
- breaks `check-clangd`, and makes clang-tidy crash on simple inputs
- likely does the wrong thing in cross builds

Also revert follow-up "[gn build] (manually) port b94db7ed (Confusables.inc)"
This reverts commit 180bae08.