Prevent removing himself from region owners if there are no other owners left

**Is your feature request related to a problem? Please describe.**

Yes, I have `max-region-count-per-player: 4` but player claims a region, adds himself to member list of it, then removes himself from owner list and then creates 5, 6, 7... and more regions in total.

**Describe the solution you'd like**

Add a permission like `worldguard.region.removeowner.self` that allows removing himself from regions IF no other owners are left in it, otherwise show error message e.g. `You can't remove yourself from this region because there are no other owners!`.

**Describe alternatives you've considered**

Remove access to remove owner command from players?..

**Additional context**