Provide salient warning when xb_stark not enabled

It looks like, work in this previous issue wasn't enough
https://www.drupal.org/project/experience_builder/issues/3528368 🐛 Add warning if XB is installed from drupal config but without xb_stark Active

It looks like, work in this previous issue wasn't enough

I wasn't aware that was in there, nice! I've run into a few instances where there was a lack of xb_stark due to recipes issues - not a manual change. It made it appear as if the UI had bugs, so it seems better to make the xb_stark dependent parts of the UI unavailable when xb_stark isn't around.

This blocks #3532265 per #3532265-3: [PP-1] Remove the `xb_dev_standard` module, instead recommend using XB's `test_site` recipe for development → .