Update Windows ext_qt to 5.9.3 and add a patch

The additional ext_qt patch fixes an issue with ANGLE WARP (software
D3D11 implementation). With this patch, ANGLE can be properly enabled on
Windows 7 systems with no proper graphics drivers installed, or when
running over an RDP connection. Similarly, QML-based dockers can now
work properly.

BUG: 386142