Add a new test ui/incoherent-inherent-impls/no-other-unrelated-errors to check E0116 does not cause unrelated errors rustc xxx (we do not know) to 1.82.0 emits unrelated errors when E0116 is present (see #125814). We do not know what caused and fixed it, but add a test to confirm rustc does not cause the same error in the future.