Clean up options and meta on uninstall

[obenland]

Proposed changes:

• Adds removals for registered user and post meta, as well as options to the uninstall hook.

Is there more data that we add, that should be removed here?

[pfefferle]

I like to cleanup in general, but this is very destructive and might cause some data loss by accident, even more because it was different before!

What about adding a consent layer when the user clicks the remove link or adding a "remove and delete all data" link?

[obenland]

might cause some data loss by accident, even more because it was different before!

This only runs when the plugin gets deleted, not when it's deactivated.
With it being different than before, do you mean that it now deletes data where it didn't use to?

What about adding a consent layer when the user clicks the remove link or adding a "remove and delete all data" link?

Core has a built-in "Are You Sure" modal when you try to delete a plugin.