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

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

> Code autocomplete works just fine with CodePatterns::None but include autocomplete does not work anymore. Gonna investigate when i have some time.

I guess the preprocessor completions are all `RK_Pattern` (added [here](https://searchfox.org/llvm/rev/2f976956e5ccef566418853015fb6b31257aa69f/clang/lib/Sema/SemaCodeComplete.cpp#10144-10150), and the `CodeCompletionResult` constructor which [only takes a `CodeCompletionString`](https://searchfox.org/llvm/rev/2f976956e5ccef566418853015fb6b31257aa69f/clang/include/clang/Sema/CodeCompleteConsumer.h#917) sets the kind to `RK_Pattern`).

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