Fix cache key collisions for paths with separators (#12159)

Closes #12158

Hashing `Path` does not take into account path separators so `foo/bar`
is the same as `foobar` which is no good for our case. I'm guessing this
is an upstream bug, perhaps introduced by
rust-lang/rust@45082b0?
I'm investigating that further.

Author: zanieb

crates/ruff_cache/src/cache_key.rs

@@ -350,7 +350,9 @@ impl<K: CacheKey + Ord, V: CacheKey> CacheKey for BTreeMap<K, V> {
 impl CacheKey for Path {
     #[inline]
     fn cache_key(&self, state: &mut CacheKeyHasher) {
-        self.hash(&mut *state);
+        for component in self.components() {
+            component.hash(&mut *state);
+        }
     }
 }