Decouple RenderingServer from as much of the codebase as possible

Notably decouples it from:
- AccessibilityServer
- DisplayServer
- Viewport
- Window

editor/editor_log.cpp

@@ -48,6 +48,7 @@
 #include "scene/gui/separator.h"
 #include "scene/main/timer.h"
 #include "scene/resources/font.h"
+#include "servers/display/display_server.h"
 
 void EditorLog::_error_handler(void *p_self, const char *p_func, const char *p_file, int p_line, const char *p_error, const char *p_errorexp, bool p_editor_notify, ErrorHandlerType p_type) {
 	EditorLog *self = static_cast<EditorLog *>(p_self);