Rollup merge of #111265 - spastorino:has_self-opaque_ty, r=compiler-errors

Make generics_of has_self on RPITITs delegate to the opaque

r? `@compiler-errors`

I couldn't come up with a test case and none of the ones in the `tests` folder is impacted by this change, but I still think is the right thing to do.

Michael, let me know if you have ideas on how to add a test that's affected by this change.

Author: Dylan-DPC