Add Block Content revision UI

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

Here's a version of #83 for anyone who needs this on Drupal 10.0.

Note it also depends on #2350939-314: Implement a generic revision UI → and #2809291-192: Add "edit block $type" permissions →

Not sure if I should be posting here or not, but I have tested a few sites, and I can't actually see any option to VIEW any revision. That is, I can use the action buttons to either revert to or delete any revision listed, but I can't actually see the revision content itself. The 'view' link that is on the node revision interface is not appearing.

@Andrew.Macpherson block content doesn't have a view route so therefore doesn't have a view revision operation either.

@acbramley correct observation but, however, without the possibility to see a revision's content: the block revision feature is quite useless