Missing functionality: pad electrical controls

[P33M]

In the C SDK, gpio_set_pulls() is implemented but other pad controls are inaccessible - I don't see any SDK functions that control output drive strength, input hysteresis (schmitt triggering) or slew rate adjustment.

c.f. 2.19.4 in the rp2040 datasheet.

[lurch]

I guess hardware_gpio would be the place to add this?

[kilograham]

Not going to make 1.2.0 unless someone wants to make a PR real quick?