Return correct HirId when finding body owner in diagnostics

[BoxyUwU]

Fixes #129145
Fixes #128810

r? @compiler-errors

fn generic<const N: u32>() {}

trait Collate<const A: u32> {
    type Pass;
    fn collate(self) -> Self::Pass;
}

impl<const B: u32> Collate<B> for i32 {
    type Pass = ();
    fn collate(self) -> Self::Pass {
        generic::<{ true }>()
        //~^ ERROR: mismatched types
    }
}

When type checking the { true } anon const we would error with a type mismatch. This then results in diagnostics code attempting to check whether its due to a type mismatch with the return type. That logic was implemented by walking up the hir until we reached the body owner, except instead of using the enclosing_body_owner function it special cased various hir nodes incorrectly resulting in us walking out of the anon const and stopping at fn collate instead.

This then resulted in diagnostics logic inside of the anon consts ParamEnv attempting to do trait solving involving the <i32 as Collate<B>>::Pass type which ICEs because it is in the wrong environment.

I have rewritten this function to just walk up until it hits the enclosing_body_owner and made some other changes since I found this pretty hard to read/understand. Hopefully it's easier to understand now, it also makes it more obvious that this is not implemented in a very principled way and is definitely missing cases :)

[compiler-errors]

💖

@bors r+ rollup

[bors]

📌 Commit ed6315b has been approved by compiler-errors

It is now in the queue for this repository.