[clang] [clang][ThreadSafety] Check trylock function success and return types (PR #95290)

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asmok-g wrote:

Hi!

Is it expected for this to fail with unique_ptrs ? We have a case in the code where the return type is an alias to unique_ptr and it's failing. Also, cases where the return type is something like 
```
absl::Nullable<std::unique_ptr<const Obj, ObjUnlocker>>
```

that is failing. Is that expected ?

https://github.com/llvm/llvm-project/pull/95290