[clang-tools-extra] [clangd] Add CodePatterns config option under Completion (PR #137613)

[Nathan Ridge via cfe-commits]

https://github.com/HighCommander4 approved this pull request.

Thanks, LGTM!

(I made one small tweak, to ConfigFragment.h, to refer to the config option values `All` and `None` with correct capitalization.)

https://github.com/llvm/llvm-project/pull/137613