Tag entity query used for promotion storage

Attaching initial patch

Maybe we should rename the tag to "commerce_promotion_available"? or "commerce_promotion_load_available", but the "load" might be unnecessary.
Other storage methods could be added at a future point making the "commerce_promotion_storage" ambiguous. Also the patch doesn't seem to apply for whatever reason.

@jsacksick could you please review the updated changes and created MR too.

Update patch to 8.x-2.39

I think "commerce_promotion_available" makes the most sense, so will merge the MR.

Automatically closed - issue fixed for 2 weeks with no activity.