Simplify solenoid settings to a global ON and a single autofire wait value

[SeongGino]

In retrospect, the way I made Solenoid Force Feedback work originally was weird;

• It assumed that the "Fast" interval was actually always faster when letting the trigger off early on a first shot.
• Autofire used an overcomplicated "Fast Interval * Multiplier" system, which required float computation
• Users complained about wondering how it worked, so very few people actually made use of the different types of "interval" values just to be able to toggle a custom AF wait factor using a solenoid command that isn't even a standard.

With this PR, we have simplified the setup to just two values:

• Solenoid ON Length determines how long the solenoid should be engaged
• Solenoid OFF Length is how long the solenoid should remain off between autofire cycles, no mult needed.

Since it was useful before, the XI1 command will now enable a runtime "autofire double length" toggle, which effectively doubles Solenoid OFF Length when enabled. XI0 will disable this flag.