[6.x] Ensure sets in imported fields can be overridden

[duncanmcclean]

This pull request fixes an issue where sets in imported Bard/Replicator fields couldn't be overridden due to the publish container's localizedFields state not being updated.

There was two things preventing the localizedFields state from updating correctly:

• The tabs watcher wasn't running when editing sets. It needed to be converted to a deep watcher.
• In ui/Publish/Field.vue, it compares the container's existing value against the updated value.
  • This condition was returning true because the Tabs.vue component was modifying the container value by reference.
  • I've fixed it by cloning the initial tabs state, preventing the reference error.

Fixes #13770