Review Route rebuild in ModuleInstaller

Is this a duplicate of #2572285: Module enabling and router rebuilding should be done in one transaction →

It's more of a revert of 📌 Rebuild routes immediately when modules are installed Fixed .

See the comments in ModuleInstaller:

if (!\Drupal::service('router.route_provider.lazy_builder')->hasRebuilt()) {
        // Rebuild routes after installing module. This is done here on top of
        // \Drupal\Core\Routing\RouteBuilder::destruct to not run into errors on
        // fastCGI which executes ::destruct() after the module installation
        // page was sent already.
        \Drupal::service('router.builder')->rebuild();
      }
      else {
        // Rebuild the router immediately if it is marked as needing a rebuild.
        // @todo Work this through a bit more. This fixes
        //   \Drupal\Tests\standard\Functional\StandardTest::testStandard()
        //   after separately out the optional configuration install.
        \Drupal::service('router.builder')->rebuildIfNeeded();
      }