[clang] [Clang SA]: add support for mismatched ownership_returns+ownership_takes calls for custom allocation classes (PR #98941)

[Pavel Skripkin via cfe-commits]

pskrgag wrote:

> Do you want to extend the scope of this PR to add some minimal docs to the attribute?
> If not, that's also fine, we will create a separate ticket for adding them later.

I am would be happy to give it a try, but I think we need to fix couple of things to truly follow the semantics. As you have already noticed, attributes conflicts on different declarations are not reported.

Also I found out that code like

```
void f21(void)
  __attribute__((ownership_returns(foo)));
```

does not cause an error. I will fill an issue for these cases.

Also, thank you so much for review!

https://github.com/llvm/llvm-project/pull/98941