Add support for micro:bit v2 internal timers

[colinvail6]

It would be nice if the internal timers on the micro:bit v2 could be used with CircuitPython (for the display so it can be multiplexed correctly)

[dhalbert]

I am not sure what you mean by the "internal timers". Could you elaborate? Since this is an nRF52840 (albeit without USB connections), whatever we support on nRF52840 in general would be supported here.

[colinvail6]

I mean the timers like TIMER0, 1, 2, 3, and 4. This should provide more of an explanation https://docs.rs/microbit-v2/latest/microbit/display/nonblocking/index.html