Refactor incompatiblity tracking for distributions (#1298)

Extends the "compatibility" types introduced in #1293 to apply to source
distributions as well as wheels.

- We now track the most-relevant incompatible source distribution
- Exclude newer, Python requirements, and yanked versions are all
tracked as incompatibilities in the new model (this lets us remove
`DistMetadata`!)

crates/pypi-types/src/simple_json.rs

@@ -89,7 +89,15 @@ impl DistInfoMetadata {
 }
 
 #[derive(
-    Debug, Clone, Serialize, Deserialize, rkyv::Archive, rkyv::Deserialize, rkyv::Serialize,
+    Debug,
+    Clone,
+    PartialEq,
+    Eq,
+    Serialize,
+    Deserialize,
+    rkyv::Archive,
+    rkyv::Deserialize,
+    rkyv::Serialize,
 )]
 #[archive(check_bytes)]
 #[archive_attr(derive(Debug))]