safe CPU-cycles with bang-bang for tools in standby

[o_lampe]

Hi duet-team
I'm not sure if we ever run into cpu overload with more'n more toolchangers. But using bang-bang for tools in standby would probably come handy then? Especially on Duet2 boards with Duex5.

Just thought I could mention it.

[dc42]

@o_lampe all Duets use hardware PWM on all the PWM-capable ports. So no CPU time is used to generate PWM. Note, this does not apply to ports of RRF to some other boards.