Set the Render Window as the parent of the Confirm On Stop confirmation
dialog when Keep Window On Top is enabled, ensuring it will always be
visible.

Previously, when Confirm On Stop and Keep Window On Top were both
enabled the Confirm On Stop dialog could be hidden by the render window
in the following situations:
* Clicking Stop in the Main Window
* Clicking the Main Window's close button
* Pressing the Stop hotkey while in FullScreen mode

This was particularly troublesome because the confirm dialog is modal,
preventing the user from moving the render window out of the way if it
was obscuring the dialog.

Fixes https://bugs.dolphin-emu.org/issues/13247.

Most of these changes are to improve consistency in capitalization.

Adds a hotkey to pause emulation and bring up the Achievements dialog.

MainWindow: Bugfix. Windows Dark mode titlebar not being set.

This reverts commit 72cf2bdb87f09deff22e1085de3290126aa4ad05.

SYSCONF settings are getting cleared when they shouldn't be. Let's
revert the change until I get proper time to figure out why it's broken.

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.

Some pieces of code are calling IsRunning because there's some
particular action that only makes sense when emulation is running, for
instance showing the state of the emulated CPU. IsRunning is appropriate
to use for this. Then there are pieces of code that are calling
IsRunning because there's some particular thing they must avoid doing
e.g. when the CPU thread is running or IOS is running. IsRunning isn't
quite appropriate for this. Such code should also be checking for the
states Starting and Stopping. Keep in mind that:

* When the state is Starting, the state can asynchronously change to
  Running at any time.
* When we try to stop the core, the state gets set to Stopping before we
  take any action to actually stop things.

This commit adds a new method Core::IsUninitialized, and changes all
callers of IsRunning and GetState that look to me like they should be
changed.

Core::GetState reads from four different pieces of state: s_is_stopping,
s_hardware_initialized, s_is_booting, and CPUManager::IsStepping.
I'm keeping that last one as is for now because there's code in Dolphin
that sets it directly, but we can unify the other three to make things
easier to reason about.

This commit also gets rid of s_is_started. This was previously used in
Core::IsRunningAndStarted to ensure true wouldn't be returned until the
CPU thread was started, but it wasn't used in Core::GetState, so
Core::GetState would happily return State::Running after we had
initialized the hardware but before we had initialized the CPU thread.
As far as I know, there are no callers that have any real need to know
whether the boot process is currently initializing the hardware or the
CPU thread. Perhaps once upon a time there was a desire to make the
apploader debuggable, but a long time has passed without anyone stepping
up to implement it, and the way CBoot::RunApploader is implemented makes
it rather difficult. So this commit makes all the functions in Core.cpp
consider the core to still be starting until the CPU thread is started.