[red-knot] Resolve symbols from builtins.pyi in the stdlib if they cannot be found in other scopes (#12390)

Co-authored-by: Carl Meyer <carl@astral.sh>

crates/red_knot_python_semantic/src/builtins.rs

@@ -0,0 +1,16 @@
+use red_knot_module_resolver::{resolve_module, ModuleName};
+
+use crate::semantic_index::global_scope;
+use crate::semantic_index::symbol::ScopeId;
+use crate::Db;
+
+/// Salsa query to get the builtins scope.
+///
+/// Can return None if a custom typeshed is used that is missing `builtins.pyi`.
+#[salsa::tracked]
+pub(crate) fn builtins_scope(db: &dyn Db) -> Option<ScopeId<'_>> {
+    let builtins_name =
+        ModuleName::new_static("builtins").expect("Expected 'builtins' to be a valid module name");
+    let builtins_file = resolve_module(db.upcast(), builtins_name)?.file();
+    Some(global_scope(db, builtins_file))
+}