uv: use ResolverEnvironment instead of ResolverMarkers

This updates the surrounding code to use the new ResolverEnvironment
type. In some cases, this simplifies caller code by removing case
analysis. There *shouldn't* be any behavior changes here. Some test
snapshots were updated to account for some minor tweaks to error
messages.

I didn't split this up into separate commits because it would have been
too difficult/costly.

crates/uv-python/src/interpreter.rs

@@ -147,7 +147,7 @@ impl Interpreter {
     }
 
     /// Return the [`ResolverMarkerEnvironment`] for this Python executable.
-    pub fn resolver_markers(&self) -> ResolverMarkerEnvironment {
+    pub fn resolver_marker_environment(&self) -> ResolverMarkerEnvironment {
         ResolverMarkerEnvironment::from(self.markers().clone())
     }