Fix: The divider for watchdog tick generation is now being set to the
source clock frequency in MHz, instead of the clock frequency in Hz.
Watchdog ticks will now be generated at 1 microsecond intervals
as intended.
* Improve clock frequency stuff for uninitialized clocks
- Made clocks singletons so the frequency handling actually works as expected
- Added initial frequencies
- Improved the docs
- Added a Clock trait
* Add pico examples.
These have the benefit of knowing which external crystal is attached.
Even though it always should be a 12 MHz crystal.
Thus we can setup the clocks properly
I also changed the rp2040 examples to work out of the box for pico boards since that will probably be used most of the time
