Playtest button and a few other changes

- Added a button in the top left of the cursed powerups menu that appears at the beginning of the game. If you click on it, you can get or change any weapons/abilities/upgrades to the level you want to test. You can also pick which of the cursed powerups if any you want to apply, and you can pick which round you start on.

- at round 7 and 12 you will face 2 and 3 skeleton bosses respectively and an increase in the difficulty of other mobs spawned as well.

- added a UI element in the bottom right to show which weapon you will switch to next

- made coins, hearts and mana drops from mobs despawn after 30 seconds. Players who got to the final rounds had tons of hearts and mana drops on the screen which allowed them to spam abilities and rarely die from mobs.

- The Godot engine updated to 4.4, so hopefully that doesn't break anything XD