Add 3X as a speed option between 2X and 4X in GameSpeed.LEVELS (#677).
Add controller hotkeys: rightshoulder (R2) cycles speed up through the
level list, leftshoulder (L2) cycles speed down. Keyboard equivalent
is hotkey 1 (cycles up). All hotkeys are gated during transitions,
scripted cutscenes, and link play (same guards as the color hotkey
at key 2).
The _cycleSpeed helper wraps the save-options update with the same
busy/overworld guard used by the existing color-cycle hotkey.
Fixes#677