Enable Pandora and Level Select with Devmode / Always allow Level Select if unlocked

This merge request makes it so that, if devmode is enabled, or if the game was started with -devparm, Pandora's Box and the Pause Menu Level Select are pseudo-unlocked. Said level select will also let you choose a level from any level select in the game, including multiplayer levels and levels you haven't unlocked yet.

Why do this? Simply put, devmode already enables you to do everything Pandora's Box and the Level Select provide via commands. However, commands aren't nearly as fast and efficient as the pause menu UI, making it so that developers are basically required to have a 100% save in order to effectively test things. This goes for locked levels as well. This really sucks, as with the new changes being made to the game for 2.2.12, there's more incentive now than ever to get all of the game's unlockables legit, but you can't do that if you already have everything unlocked due to a 100% save file you downloaded just so you could test things more efficiently. But with this, now you can easily access everything a developer could want right from the comfort of the pause menu.

As a bonus, the Pause Menu Level Select will now always be enabled if the Main Menu Level Select is unlocked. Not quite sure why this wasn't the case already.