style: freeze the resolved-catalogs carrier

Nothing mutates it between resolve and commit, so there is no reason to
pay for the runtime borrow flag a mutable pyclass carries — the same
reasoning that froze PhysicalOptimizerRules and ResolvedTables.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: timsaucer

crates/core/src/context.rs

@@ -1927,8 +1927,9 @@ struct ResolvedTable {
 
 /// Catalog providers imported for a `with_extensions` call.
 ///
-/// Opaque to Python, like [`PyResolvedTables`] and [`PyPhysicalOptimizerRules`].
-#[pyclass(name = "ResolvedCatalogs", module = "datafusion._internal")]
+/// Opaque to Python, like [`PyResolvedTables`] and [`PyPhysicalOptimizerRules`],
+/// and `frozen` for the same reason as both: the commit only reads.
+#[pyclass(frozen, name = "ResolvedCatalogs", module = "datafusion._internal")]
 pub struct PyResolvedCatalogs {
     catalogs: Vec<(String, Arc<dyn CatalogProvider>)>,
 }