Allow loading Skiko in more than one classloader.

Fixes https://github.com/JetBrains/compose-jb/issues/785.

Updated to a cleaner interop plugin syntax

* Fix window.layer.focusTraversalKeysEnabled = false

Disabling focus keys didn't work

Test:
```
    window.layer.focusTraversalKeysEnabled = false
    window.layer.addKeyListener(object : KeyAdapter() {
        override fun keyPressed(event: KeyEvent) {
            println("keyPressed")
        }
    })
```

Press Tab or Shift-Tab. Before fix there was no output in console

* Remove unused import

```
window.preferredSize = Dimension(800, 600)
window.pack()
window.layer.awaitRedraw()
window.isVisible = true
```

* Added getting [windowHandle] and [contentHandle].

* Added getting windowHandle on Linux.

More flexible adapter selection in Metal and DirectX rendering via properties (skiko.metal.gpu.priority, skiko.derectx.gpu.priority).

Use macos-11.0 explicitly

Added OS/JRE info in debug output.