[fence_manager, ui] antiflicker fix + toggle integration (#4004)

tldr: we (me and maran) found the missing piece to make delay_fence and should_flush coop and cover all remaining flicker issues tested so far.
the lil change is in src/video_core/fence_manager.h
the rest is toggle stuff.

END

(credits rolls up)

post credits scene for the toggle drama:

i've been forced to use custom builds for around 1 year now, coz gpu mode above fast was pulling performance down yet not covering flicker entirely in most games tested. and we know that it's a mess to rely on gpu mode as it brings along a bunch of undesired stuff.
i need this toggle. and i've seem far less relevant before, so hey, gimme this one so i can call it mine :3

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4004
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>

src/qt_common/config/shared_translation.cpp

@@ -193,6 +193,9 @@ std::unique_ptr<TranslationMap> InitializeTranslations(QObject* parent) {
     INSERT(Settings, skip_cpu_inner_invalidation, tr("Skip CPU Inner Invalidation"),
            tr("Skips certain cache invalidations during memory updates, reducing CPU usage and "
               "improving latency. This may cause soft-crashes."));
+    INSERT(Settings, antiflicker, tr("Anti-Flicker"),
+           tr("Forces GPU fence callbacks to wait for submitted GPU work.\n"
+              "Use with Fast GPU mode, to avoid flicker with lower performance impact."));
     INSERT(Settings, vsync_mode, tr("VSync Mode:"),
            tr("FIFO (VSync) does not drop frames or exhibit tearing but is limited by the screen "
               "refresh rate.\nFIFO Relaxed allows tearing as it recovers from a slow down.\n"