[clang] [LifetimeSafety] Add suggestion and inference for implicit this (PR #176703)

[Utkarsh Saxena via cfe-commits]

usx95 wrote:

Can you please do a rebase. I think after https://github.com/llvm/llvm-project/pull/176805, we could also target field accessors as well
```cpp
struct S{
std::string s;
std::string_view getS1() /*lb suggestion here*/ { return s; }
std::string_view getS2() /*lb suggestion here*/ { return this->s; }
}
```

https://github.com/llvm/llvm-project/pull/176703