Revert "Stop running the test while it's failing"

This reverts commit a084303c91fca4c4a14a31a30d8c15f001665611.
Merge branch 'develop' of github.com:saltstack/salt into hotfix/immutable-lists-sum
Merge branch 'develop' of github.com:saltstack/salt into hotfix/immutable-lists-sum
Test `ImmutableList` sum
Revert previous intrusive fixes
No more proxied immutables. Add test for nested immutables.
Also test slicing
Merge pull request #11413 from s0undt3ch/hotfix/immutable-lists-sum

Simpler immutable types