Transition to salsa coarse-grained tracked structs (#15763)

## Summary

Transition to using coarse-grained tracked structs (depends on
https://github.com/salsa-rs/salsa/pull/657). For now, this PR doesn't
add any `#[tracked]` fields, meaning that any changes cause the entire
struct to be invalidated. It also changes `AstNodeRef` to be
compared/hashed by pointer address, instead of performing a deep AST
comparison.

## Test Plan

This yields a 10-15% improvement on my machine (though weirdly some runs
were 5-10% without being flagged as inconsistent by criterion, is there
some non-determinism involved?). It's possible that some of this is
unrelated, I'll try applying the patch to the current salsa version to
make sure.

---------

Co-authored-by: Micha Reiser <micha@reiser.io>

crates/ruff_db/src/parsed.rs

@@ -73,6 +73,14 @@ impl std::fmt::Debug for ParsedModule {
     }
 }
 
+impl PartialEq for ParsedModule {
+    fn eq(&self, other: &Self) -> bool {
+        Arc::ptr_eq(&self.inner, &other.inner)
+    }
+}
+
+impl Eq for ParsedModule {}
+
 #[cfg(test)]
 mod tests {
     use crate::files::{system_path_to_file, vendored_path_to_file};

crates/ruff_db/src/testing.rs

@@ -18,7 +18,7 @@ pub fn assert_function_query_was_not_run<Db, Q, QDb, I, R>(
 
     db.attach(|_| {
         if let Some(will_execute_event) = will_execute_event {
-            panic!("Expected query {query_name}({id}) not to have run but it did: {will_execute_event:?}");
+            panic!("Expected query {query_name}({id}) not to have run but it did: {will_execute_event:?}\n\n{events:#?}");
         }
     });
 }
@@ -46,7 +46,7 @@ pub fn assert_const_function_query_was_not_run<Db, Q, QDb, R>(
     db.attach(|_| {
         if let Some(will_execute_event) = event {
             panic!(
-                "Expected query {query_name}() not to have run but it did: {will_execute_event:?}"
+                "Expected query {query_name}() not to have run but it did: {will_execute_event:?}\n\n{events:#?}"
             );
         }
     });