Feature: Show Modloader Achievement UI in the vanilla achievements menu

[KnightMiner]

Mockup:

To the end user, this should seamlessly show modded achievements with vanilla achievements.

Internal details

When clicking the mod button, a mod UI will pop up, covering the title and all vanilla achievments (suppressing tooltips). In addition, the selected vanilla achievements will need to be covered so it no longer looks selected.

All four buttons at the bottom should behave as expected when in the mod achievement UI, that is:

• For the true achievements menu (either squads or global), clicking it closes the modded UI and reveals the vanilla one
• For the unseleced vanilla menu (the other of global or squads), clicking it should update the vanilla menu and close the mod UI. Can probably accomplish this by having the mod UI close if the vanilla UI it was opened under closes
• Clicking the mod button again does nothing
• Clicking close should close the vanilla screen and the modded overlay. Can accomplish this in the same way as above, close the modded screen if the vanilla one changes

Can probably just reuse the modloader achievements UI from the main menu.