[clang] [clang][ast][objc] Implement getNameForDiagnostic for ObjCMethodDecl and ObjCPropertyDecl. (PR #213030)

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dmaclach wrote:

@ahatanak could you take a look at this, or possibly suggest someone else appropriate? I totally get that it's a little retro these days to be making ObjC changes, but I am looking to improve include-cleaner diagnostics and this seemed to be the cleanest way to do it, and should improve diagnostics elsewhere as well for us folks still maintaining ObjC codebases.

https://github.com/llvm/llvm-project/pull/213030