Mark more tests with @group #slow and remove it from some others

https://git.drupalcode.org/project/drupal/-/jobs/2165814 is down to 3m41 with the couple of User tests added to the slow #group, so that's also about 20 seconds down now.

Now that Rest XML tests skip methods more efficiently, there are some tests that don't stick out as slow any more, so we can remove the group from those - that balances out adding more to the group a bit.

Seems straight forward

Backported down to 10.3.x to keep things in sync.

Committed and pushed 745a0e25dc to 11.x and 42b28e4855 to 11.0.x and b74f2b159f to 10.4.x and f59d1e0cac to 10.3.x. Thanks!

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