Common patterns rewrite

slowN_pattern, normalN_pattern, and onN_pattern for N=(1..4)
rewritten to be brightness-independent, and to avoid switching
multiple outputs on at once, if possible.
If not (such as when PWMLED 2 is continuously on), use mode 2 and 3
with the same target current to accomodate for different battery voltages
when more than one output is running.

TODO: actually set brightness based on various conditions, such as
ambient lights, user-requested dim mode, etc.