[clang] Performance optimizations for function effects (nonblocking attribute etc.) (PR #96844)

[Doug Wyatt via cfe-commits]

dougsonos wrote:

Added a further tweak: add a bool to ASTContext to track whether any FunctionProtoType's with effects have been created, so that Sema can short-circuit checks involving effects when it knows no one has any. This seems to have the desired effect of only paying for the feature when it's in use.

https://github.com/llvm/llvm-project/pull/96844