Add an amount argument to the minion give command

[Crispi2k24]

What changed

/minions give <type> takes an optional amount: /minions give miner 10. The two existing forms keep working and now route through the same method with an amount of one.

MinionItemFactory#create gained an overload that takes the amount.

Why

Handing out more than one minion meant repeating the command, which is tedious when setting up a server or paying out a reward.

Minion items carry no per-item data, so they stack, and Inventory#addItem already splits an oversized stack across slots. The amount therefore belongs on the item the factory builds - the factory owns how a minion item is put together, including how many of it there are - and the command stays a single addItem call.

Testing / notes

./gradlew build passes. Verified on a Purpur 26.2 server: /minions give miner 10 gives ten across stacks, /minions give miner still gives one, /minions give still gives one of the default type, and an unknown type still reports the same message as before.