Rollup merge of #113453 - spastorino:new-rpitit-30, r=compiler-errors

Remove unused from_method from rustc_on_unimplemented

Fixes #113439

`on_unimplemented_note` was calling `item_name` for RPITITs and that produced ICEs. I've added a regression test for that but also have removed `from_method` symbol entirely because it wasn't even used and by doing that the `item_name` call was also removed.

r? ``@compiler-errors``

Author: compiler-errors