Windows: fix EndOfMedia handling in the MediaEngine player

- play() from EndOfMedia no longer seeks to 0 before Play(): Play() on
  an ended engine restarts from the beginning anyway, and the explicit
  seek made the engine report ENDED again right away.
- Ignore PAUSE events that arrive after playback was resumed. Engine
  events are delivered queued, so e.g. setPosition() followed by play()
  from EndOfMedia briefly switched the player to PausedState.
- Reset the buffer progress to 0 at EndOfMedia.
- pause() from EndOfMedia rewinds to the beginning via setPosition(0)
  and switches to BufferedMedia, like play() does.

This makes processEOS pass, so unskip it.

Change-Id: Id120793689c7f88f29c8392a802a07a5f0f16c61
Reviewed-by: Tim Blechmann <tim.blechmann@qt.io>