Rollup merge of #90386 - pierwill:assert-incr-state-85864, r=Aaron1011

Add `-Zassert-incr-state` to assert state of incremental cache

Closes #85864.

compiler/rustc_interface/src/tests.rs

@@ -636,6 +636,7 @@ fn test_debugging_options_tracking_hash() {
 
     // Make sure that changing an [UNTRACKED] option leaves the hash unchanged.
     // This list is in alphabetical order.
+    untracked!(assert_incr_state, Some(String::from("loaded")));
     untracked!(ast_json, true);
     untracked!(ast_json_noexpand, true);
     untracked!(borrowck, String::from("other"));