perf(2meet-data-optimizer): keep cached routed counts across unrelated post meta writes

- cached counts followed posts' last_changed, which WordPress moves on any
  post meta write; themes write meta on page views (on dev36 Blocksy saved a
  dynamic-CSS descriptor for each listing a crawler visited), so the cache
  was invalidated every few seconds and keyword/filter searches recounted
- counts now follow their own last_changed group (tmdo_posts), bumped on
  clean_post_cache (post saved or deleted; hooked in every mode) and on flat
  writes through the Hook Bus, plus terms' last_changed; a routed search reads
  no unmanaged meta
- Verify: PostQueryRouterFoundRowsTest (unrelated meta write keeps the count,
  save or flat write recounts), integration 588, unit 703, phpcs, stan;
  dev36 front-end
- PR: PR-117 (2.3 acceptance)

includes/engine/class-tmdo-hook-bus.php

@@ -912,6 +912,7 @@ final class TMDO_Hook_Bus {
 	private static function touch_posts_last_changed( string $type ): void {
 		if ( 'post' === $type ) {
 			wp_cache_set_posts_last_changed();
+			TMDO_Post_Query_Router::bump_count_version();
 		}
 	}