The 3D viewer also uses OpenGL, so it also needs to
adjust based on DPI scale factors.
This patch moves the 3D viewer common config code solely
within the 3D viewer, and adds handling of the DPI scale. This
also avoids duplicated logic in PCB_BASE_FRAME::CommonSettingsChanged.
For now, as EDA_3D_VIEWER is not included in the Kiway settings
dispatch, still manually invoke the settings update from
PCB_BASE_FRAME.
The PANEL_3D_PREV gets a similar function to read the config, but
it doesn't have a listener for the update, so it's set just once
at dialog init, just like the existing pan settings.
Fixes: lp:1823681
* https://bugs.launchpad.net/kicad/+bug/1823681
124dd5e59a