The V-Sync option is fundamentally broken in Citra, so let's do the same as yuzu and remove it entirely for SDL2 and at least from the frontend for QT.
(It was also only used by 7.3% of users)
citra-qt: Add customizable speed limit target
* Update SDL config for the new frame_limit option
* Made max lag time a function of target speed percent.
* Added a checkbox to enable/disable frame limiter
* UI: Prevent frame_limit from under/overflowing
* UI: Hide target speed percent when frame limiter is off
* Disable frame limit spin box when framelimit isn't enabled
