Prevent more spurious unreachable pattern lints
Continues the work of https://github.com/rust-lang/rust/pull/115937 by introducing `PatKind::Error`, to be used instead of `PatKind::Wild` when an error was raised during pattern lowering. Most of match checking lints are skipped when a `PatKind::Error` is encountered. This avoids confusing extra warnings when a pattern is malformed. Now `PatKind::Wild` should indicate an actual wildcard pattern.
r? `@oli-obk`
7d1b24f4bc