Improve world regeneration command.

[TraceLTRC]

Fixes #2783, also fixes an unwanted behaviour where the spawn on regenerated worlds stays the same when providing a new seed.

When fixing #2783, I don't know if I'm allowed to modify the classes in the API package. If this shouldn't happen, we could always make the deleteWorldFolder boolean to keep the paper config instead of deleting all files in the directory if set to false.

[FakEEE14]

hi this is very nice thing, why it's not approved yet ?

[zax71]

We are trying to get development back on track internally. As soon as we can review the code as a team this will get merged :)

[FakEEE14]

thanks sir

[pjindras]

Any update in this case? I would greatly appreciate this improvement :D