[clang] [clang][analyzer] Clear `ObjCMethodCall`'s cache between runs (PR #161327)

[Balázs Benics via cfe-commits]

balazs-benics-sonarsource wrote:

I remember debugging this. Fun times.
I wonder if we could do even better by smuggling in some reference to that helper function, so we could move that global into a field. E.g. as a sibling of the allocator pool.

https://github.com/llvm/llvm-project/pull/161327