refactor metaparam scopes to groups, preset toggles, and sprd

[andr-ew]

rather than scope there are two settings per metaparam:

• grp: select one of four(/6) control groups with a unique value
• prst: (on/off) randomized preset values unique to this group are used

the prst selector on the grid controls the prst of a particular grp (not track). if no metaparams are prst’ed for a particular grp, it will not be displayed

each metaparam comes with a sprd setting, which sets the scale of a track-specific offset:

• track 1: -50% of the range
• track 2: 50% of the range
• track 3: -25% of the range
• track 4: 25% of the range

the function of K2/3 changes depending on the value of prst:

• prst off: <-> - hold to adjust sprd (norns or arc)
  • if only a single track is assigned to the group, do nothing
• prst on: x - randomize active prst value

we’ll go ahead and implement these changes on windowparams as well

• separate settings for start & length
  • main use case is using presets for start but not length, or vice versa
• whenever 2+ tracks share the len group, special behavior applies and looping is triggered from the lua layer to keep tracks in sync
  • each trigger frequency operates on a multiple/division of the octave selection for the track. faster tracks retriggered faster, slower tracks retriggered slower

[andr-ew]

the groups should be labelled a - d/f to attempt to prevent conflation with track numbers