…separate scripting and UI. implement it for JS

… it to override score gfx

…tartup on win32

…ustom apps

…ed with a compatible() function

…change

Necessary for JS which can have external UI or not depending on its script

Default font is now IBM Plex which is much more readable on Win32

…andled at a single place

- Have a single engine per-thread with distinct QQmlContext instead
  of one engine per object
- Fully implement custom UI support
- Add new API for storing & retrieving state of JS objects across restarts and
  communicating between UI and execution.
- Whenever possible, load QML files from disk to trigger the disk cache, which will
  enable much faster loading / reloading on the execution thread
- Make sure that engines respect import paths, and change presets to use a qmldir to import JS files,
  so that we do not hit QTBUG-107204