iOS. Use `nativeScale` instead of `scale` when we pass events to Compose, and create the Canvas for Compose

[igordmn]

We should use value * uiview.nativeScale for:

1. the draw buffer size in pixels (see MetalContextHandler.kt and SkiaLayer.ios.kt)
2. the ComposeScene size
3. the event position sent via scene.sendPointerEvent

Now we use scale. If it is different from nativeScale - it leads to resizing artifacts.

We should use uiview.scale for:

1. the density of ComposeScene.density (it is used when we use 354.dp in Compose)

To do all that, we need to change public API of skiko as well. One of the solutions:

• SkiaLayer.contentScale - still returns scale (but it isn't used for internal calculations)
• SkikoPointerEvent.x - return pixels instead of pointers, calculated via nativeScale
• we don't multiply SkikoPointerEvent.x, just send it directly to scene.sendPointerEvent

[okushnikov]

Please check the following ticket on YouTrack for follow-ups to this issue. GitHub issues will be closed in the coming weeks.