make window position and size interpolate smoothly and independently …

[mieldepoche]

…of framerate

Updates the window position and size in _process instead of _physics_process and replace lerps with a framerate-independant interpolation function.

• this takes more resources on high refresh-rate monitors, but it should really not be a problem considering it's very small and that window movement and resize only happen usually when the game is paused.
• I adjusted the interpolation weights to be much faster than the current behavior (the current behavior felt waay too slow and heavy to me). Those could be exposed as settings maybe, but that would be overkill I think.
• I don't know what the "animation" is in regard to windows (there's position, size, and a special "animation" case). I chose a slow speed randomly, but it may not be fitting.