The GHOST_DisplayManager and its implementations are for the most part
unmaintained and almost completely unused in all backends. To clean
things up, and avoid any confusion about how displays are handled in
each respective GHOST backend, this PR completely removes the GHOST
Display Manager, and move the few remaining logic it still held directly
to the corresponding backends.
The backends that were modified (apart from removing the display manager
initialization call from their init) are:
- Win32: `GHOST_SystemWin32::getNumDisplays()` was calling
`m_displayManager->getNumDisplays`, the underlying system metric call
(`GetSystemMetrics(SM_CMONITORS)`) was substituted in place.
- SDL: `GHOST_SystemSDL::createWindow` was calling
`GHOST_DisplayManagerSDL::getCurrentDisplayModeSDL` which returned its
`m_mode` data member by reference. Since none of the
`GHOST_DisplayManagerSDL` member function that modified this data member
were ever called, the variable `memset` initialization call was
substituted in place from the `DisplayManagerSDL` constructor
Pull Request: https://projects.blender.org/blender/blender/pulls/138066
733d65e514