* Add sublabels for "port x controls" entries
Due to the port-specific indexes, sublabels for these entries
are handled specially. Some simplification/generalization was
applied and hand-crafted string joining was removed from a few
places, though it remains still in other places.
Preparation for #16121 (this commit does not do anything yet with
file names).
* Further simplifications around joypad_index
Removed a few labels, now unused, and the left/right check, as it
fell back to the default which is given anyway in advance.
Adds support for sub-frame shaders to vulkan/glcore/dx10-11-12.
Builds on the concept already present for frame duplication in use for BFI, to present multiple 'sub' frames per real frame to the shaders, so they can run at a higher framerate than the content framerate. Must be enabled via subframe shaders setting under synchronization settings to be active.
Will allow BFI to be implemented inside of the shaders, among any other use for the higher framerate shader authors can devise.
CurrentSubFrame and TotalSubFrames have been available inside the shaders to track what they want to do on an given subframe. TotalSubFrames will always be 1 when the setting is disabled (and when in menu/ff/pause). Framecount will not increment on sub-frames, as it does not for injected bfi frames now. Should not interfere with any existing shaders that do not check for subframes.
Loading the last used disc for multi-disc content was automatic.
However, in some cases it is not wanted, as described in #16018
Option is added for controlling the function. Disabling the
option will also implicitly disable index saving.
The check for sleeping to sync to a specific speed that is meant for fast forward/vrr could be true for a non-vrr normal core running state causing a possible sleep in a situation it was not intended for, especially at higher hz, and thus interfering with frame pacing.
