Qt: Skip emulator-specific things on startup if starting in manager mode:

- Don't try to read 86box.cfg;
- Don't initialize subsystems that aren't used in manager mode;
- Ignore `-I` or `-X` command-line options;
- Don't block keyboard navigation and mnemonics in menus;
- Don't perform UUID/WinBox/cpu_override checks.

src/qt/qt_styleoverride.cpp

@@ -22,6 +22,10 @@
 #include <QIcon>
 #include <QStyleOption>
 
+extern "C" {
+#include <86box/86box.h>
+}
+
 #ifdef Q_OS_WINDOWS
 #include <dwmapi.h>
 #ifndef DWMWA_USE_IMMERSIVE_DARK_MODE
@@ -37,7 +41,7 @@ StyleOverride::styleHint(
     QStyleHintReturn   *returnData) const
 {
     /* Disable using menu with alt key */
-    if (hint == QStyle::SH_MenuBar_AltKeyNavigation)
+    if (!vmm_enabled && (hint == QStyle::SH_MenuBar_AltKeyNavigation))
         return 0;
 
     return QProxyStyle::styleHint(hint, option, widget, returnData);