Refactor internals of CelesteTAS

[psyGamer]

No description provided.

[LozenChen]

1. CelesteTAS-EverestInterop/CelesteTAS-EverestInterop/Source/EverestInterop/Core.cs

   Line 99 in 872c7a7

   if (Engine.FrameCounter % (ulong)Manager.PlaybackSpeed == 0) {

   
   This leads to a DividedByZero exception when playback speed is slow (so it rounds down to 0)
   Can reproduce this by pressing "\", the default slow forward hotkey

2. It seems if you put a breakpoint, then the tas is saving states EVERY FRAME before that breakpoint

3. If we press FrameAdvance when the tas is running normally, we can't go into FrameAdvance now (previously we can), this doesn't feel right

4. If we put a breakpoint, then "RightCtrl" (the default Start/Stop hotkey) doesn't really work