No form validation if start date is greater than end date

Marked the following as duplicates

• 🐛 No form validation if start date is greater than end date Closed: duplicate
• 🐛 Alpha widget no error for end date before start date Closed: duplicate
• 🐛 Alpha widget throws exception when end date is before start date Closed: duplicate

The tests from this one are conflicting with the tests added a few days later in #3074571: Alpha widget doesnt adjust time zone properly → . It looks like both the alpha test in this issue and the other issue are based of DateRecurModularOscarTest added a number of months earlier, which is why the merge/diff is a bit whack.

Tests above are red, needs a reroll.

I'd start with the tests committed then copy over tests from this issue or Sierra.

Can we get a MR.

Thanks

MR opened. I can see that the build looks like it will fail with an error that Drupal\date_recur_entity_test\Entity\DrEntityTest does not exist. I can say locally with a feature branch off of 3.2.x that this class does exist and Drupal\date_recur_entity_test\Entity\DrEntityTestBasic does not, which is why I "fixed" this in my MR. Not sure what's going on there.