Support adding/removing multiple resource packs

[mergu]

I'm a bit rusty here so apologies if anything is flat out wrong.

This was all tested on 1.21.4, multiple rps can be added and removals work:

I wasn't sure how to format the command with removals.. my guess is url/hash would become optional args and the meta would need to explain the differences. I just opted for some mecs

[mergu]

fixed format

[tal5]

Marking this as a draft for now, feel free to mark as ready for review once comments are addressed.

[mcmonkey4eva]

Closing to de-clutter PR list, when this can be finished let us know and we'll reopen.