Stability hotfix — Celestial Golf Steam update #949842

This is a hotfix for a rare but significant bug:Fixed memory leaks which could lead to major graphical glitches. After playing for some amount of time, UI and game elements would disappear or start showing garbage. (The amount of time was dependent on in-game activity and framerate; faster computers experienced this sooner.)And a few other bugfixes:Fixed: Tutorial skips two screens when pressing Space/Enter.Fixed: Unlocked tutorials don't appear in list until level change.To ensure stability and improve future bug reporting, I took the opportunity to make a few other tweaks, without any gameplay changes:Windows-only: switched graphics API from Vulkan to Direct3D 12. This should have no noticeable effect, but was strongly recommended by the Godot team due to various video driver bugs in Vulkan. In the event of a graphics issue, you can switch back by going to game Properties in Steam, and...