[clang-tools-extra] Use spelling for clangd missing includes filtering (PR #143411)

[kadir çetinkaya via cfe-commits]

kadircet wrote:

sorry for silence here, i was mostly waiting for some replies to https://github.com/llvm/llvm-project/pull/140594#issuecomment-2958066558. as it stands, i feel like we'll likely limit users with a spelling based filter. unless people have concerns/disagreement, i'd suggest we resolve this by filtering on resolved paths.

https://github.com/llvm/llvm-project/pull/143411