[clang] [clang-format] Limit how much work guessLanguage() can do (PR #78925)

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

> @HighCommander4 see #82911

Thanks. I've prototyped the clangd changes on top of this, and it seem to be working (i.e. successfully avoiding the OOM for workflows that don't involve formatting the file). I've pushed the changes to my fork at https://github.com/HighCommander4/llvm-project/tree/issue-1384-alternate; I will submit them for review once the dependent patch merges.

https://github.com/llvm/llvm-project/pull/78925