Fix missed `RenderDevice::configure_surface` call on window size change

[HackerFoo]

Objective

On iOS devices, the old code would sometimes miss changes and not call RenderDevice::configure_surface appropriately, leaving the screen at the wrong size when rotating.

Solution

Change the ExtractedWindow::size_changed field to a size_change_pending flag that is only cleared after calling configure_surface.

Changelog

Fixed: Windows may not be configured on size changes.

[alice-i-cecile]

@HackerFoo this needs to be rebased following windows-as-entities.

[NthTensor]

Can anyone still reproduce this? It's quite old.

[bas-ie]

Backlog cleanup: closing due to inactivity. Probably best to wait for a further bug report if this is still an issue 2 years down the track.