Support vsync in all hardware backends, support runtime update

[unknownbrackets]

This does a few things:

• Uses FIFO on Vulkan when vsync enabled, assuming this will be more reliable than MAILBOX.
• Forces frameskip for unthrottle on Vulkan when vsync enabled.
• Skips vsync for all other backends when unthrottled (like OpenGL.) Fixes D3D vsync prevents unthrottle from working right (plus, fixed hotkey bug) #7929.
• Enables vsync on Direct3D 11. Fixes dx11 vsync not implemented #12493.
• Ensures all backends can enable/disable vsync without a restart (previously D3D 9 required a restart.)

-[Unknown]

[hrydgard]

Looks good!

[ghost]

Finally no micro stuttering anymore.

[unknownbrackets]

Probably, the affect on OpenGL was because I moved the vsync interval setting to BeginHostFrame, where it should've been. That just means the driver didn't like when we were updating the value, I guess.

That's not relevant to the other backends, though, because their APIs are different.

-[Unknown]

[ghost]

Also , Vsync on DX9 no longer disables the "unthrottle" button from working.
Previously it was always stuck on 60 fps even if you tried to unthrottle.
Dunno if it fixes any issue here but just pointing out.

[unknownbrackets]

That's what "Skips vsync for all other backends when unthrottled (like OpenGL.) Fixes #7929." meant.

-[Unknown]