SDK / exoplayer

There were two bugs in StyledPlayerControlView:
- Center icons are shown when toggling control view in minimal mode.
- `StyledControlView#setShow{*}Button` methods and corresponding
  `set_show_*_button` attributes didn't work properly.

This CL fixes bugs by controlling the buttons' visibility in one place,
StyledPlayerControlViewLayoutManager.

PiperOrigin-RevId: 326567213