Adapt Miri to the overhauled filename handling

And use the diagnostic method for diagnostic paths.

Author: Urgau

src/tools/miri/src/diagnostics.rs

@@ -616,7 +616,7 @@ pub fn report_msg<'tcx>(
                 err.subdiagnostic(frame_info.as_note(machine.tcx));
             } else {
                 let sm = sess.source_map();
-                let span = sm.span_to_embeddable_string(frame_info.span);
+                let span = sm.span_to_diagnostic_string(frame_info.span);
                 err.note(format!("{frame_info} at {span}"));
             }
         }