Dolphin already uses QStyleHints::colorScheme to detect dark mode,
so this code is now redundant.

bugfix:  SetQWidgetWindowDecorations(this); not called before show() for Windows darkmode titlebars.

The actual call to (QWidget) show() needed to come sooner. Show() was originally left alone, but with other checks needing to move with (QWidget) show(), this function became less useful.  Show()  was originally created to fix the render widget appearing behind the main window, but that appears to work fine in this iteration.

Built-in assembler for debugger interface

This widget will be used in several places to notify the player that a feature has been disabled because hardcore mode is on. It includes a button to open the Achievement Settings so that Hardcore Mode may be turned off. Also included is the framework required to open AchievementsWindow specifically on the Settings tab.

Disable right-click menu on main window

Before, right-clicking on the toolbar would allow toggling all dock widgets, including the debugger ones even when they are disabled. (See https://doc.qt.io/qt-5/qmainwindow.html#createPopupMenu for this behavior, and https://bugs.dolphin-emu.org/issues/13306 for an example of where it caused issues.)