[clang] [clang][DebugInfo] Emit DW_AT_object_pointer on function definitions with explicit `this` (PR #122897)

[Adrian Prantl via cfe-commits]

adrian-prantl wrote:

> @dwblaikie @adrian-prantl any thoughts on adjusting the DWARF spec to allow explicit `this` parameters to be non-artificial but still be valid `DW_AT_object_pointer`s?

I would suggest posting an issue to dwarf-discuss that just turns that into

```
Many languages make the object pointer an implicit parameter with no syntax. In that case the parameter should have a DW_AT_artificial attribute whose value is true.
```

and give an example. Also maybe of a language like Python where self is quite explicit.

https://github.com/llvm/llvm-project/pull/122897