The Vivante GPU on many STM32MP1 based boards does not support sRGB
as an internal format.
Introduce a check for sRGB support and default to `RGBA8` internal format
if not supported.
Additionally the STM32MP1 needs to be checked for `GL_ARB_vertex_array_object`
Closes#1991
* Bug fix: reset repaint countdown when we pass it
* eframe: debug-print what winit event caused a repaint
* egui-winit: don't repaint when only moving window
* fix docstring
