WIP: Support Qt 6 by porting to Qt Quick Controls 2 and Qt Labs Platform

[Vogtinator]

• [ ] Test on various platforms
• [ ] Fix FlashDialog sizing (initial and minimal size)
• [X] Enable Qt6 builds
• [ ] Fix Qt6 build for Android
• [ ] Fix the Qt6-win64 build in wine:

0140:err:d3dcompiler:D3DCompile2 Failed to compile shader, vkd3d result -4.
0140:err:d3dcompiler:D3DCompile2 Shader log:
0140:err:d3dcompiler:D3DCompile2     <anonymous>:3:45: E5000: syntax error, unexpected '(', expecting ';' or ','`