Add datapack management to worlds

[Madis0]

MultiMC supports world and resource pack management, the next thing could be managing the datapacks of a world.

A separate window for a world that looks similar to resource pack management.

Steps to use the suggested feature:

1. Right click an instance > Edit instance
2. Click "Worlds"
3. Click a world
4. Click "Datapacks"
5. A new window would open that lets the user manage their datapacks for a world.

[peterix]

Could maybe just be a button that opens the folder in the system file manager at first.

[peterix]

Yay. added that.

There's more to manage here though.

Apparently, the datapacks have order to them, which is stored in level.dat. This is version specific, so we should only allow all of this on versions that DO support datapacks, and possibly version the feature itself based on the world version.

Complexity.

For now, just opening the folder should remove a few clicks from the process.

[ReubenBL]

I'd love for data pack management to be added. Tried to make a world with a simple advancement datapack in it and it simply would not generate the world.