macOs, Windows. draw in a background thread

fixes 1) and 3) in https://github.com/JetBrains/skiko/issues/76

also fixes slow event dispathing in Compose (it is because vsync blocked AWT thread)

redrawImmediately is more right choice here, we don't need to repaint entire window

Fix "open windows stress test"

There were NullPointerException.

Also rename dispose to disposeCanvas.

And add method "dispose" for full dispose

Using an integrated video card on Metal rendering

Fix dialog bugs

Make HardwareLayer internal. It doesn't provide any API now, and when it does - we can provide it in SkiaLayer.

Added API to get the current SkiaLayer graphics API.