Rollup merge of #114670 - compiler-errors:issue-114660, r=cjgillot

Don't use `type_of` to determine if item has intrinsic shim

When we're calling `resolve_instance` on an inline const, we were previously looking at the `type_of` for that const, seeing that it was an `extern "intrinsic"` fn def, and treating it as if we were computing the instance of that intrinsic itself. This is incorrect.

Instead, we should be using the def-id of the item we're computing to determine if it's an intrinsic.

Fixes #114660

Author: matthiaskrgr