[Snapshot & Restore] UI locks into a step under certain conditions

[jloleysens]

Kibana version:

8.0.0

Describe the bug:

When editing a snapshot policy in Snapshot & Restore UI and clicking through different steps a user can wind up in situation where the form "locks" them into a step.

Steps to reproduce:

1. Start editing or creating a snapshot policy
2. On the "settings" page create an invalid configuration by selecting 0 indices (this should correctly invalidate the form and indicate that you need to select at least one policy)
3. Go back to step one of the wizard
4. You should be stuck on step 1 (i.e., step-wise navigation is disabled and the "next" button is disabled)

Expected behavior:

The wizard should not lock you into a step if there are errors you cannot address on that step.

Any additional context:

This looks like it is stemming from the "global" validation state and "maxCompletedStep". Errors are not per step and so the UI has no way of locking a user into the step where the error. This approach has the drawback of potentially locking a user into a step where errors cannot be addressed.

Current work around is to just refresh the page to get rid of any hidden invalid state - not ideal :(

[elasticmachine]

Pinging @elastic/es-ui (Team:Elasticsearch UI)