A simple_pwm update event interrupt to be able to synchronize with pwm

[smeenka]

To able to synchronize with a pwm (for example sample motor current with ADC) I propose hereby an update interrupt for simple_pwm.
A test can be found in stm32g0 example directory, which shows the functionality.

[Dirbaio]

examples don't use cargo-embed, please don't add an Embed.toml

[smeenka]

Will remove. Also change the implementation, not to use the global static signal, but a signal in interrupt state context

[smeenka]

Added a reset function to pwm to be able to synchronize multiple timers to have the same phase.

[Dirbaio]

LGTM, except could you change State to contain an AtomicWaker instead of a Signal? t's slightly faster/smaller.

This means you'll have to use a manually-written poll_fn from the non-interrupt code:

• Enable interrupt
• poll_fn that does
  • register waker
  • if interrupt flag is set, clear it, return Poll::Ready
  • else return Poll::Pending

and the interrupt handler doe

• disable interrupt (NOT clear the interrupt flag like you'd usually do, leave it there so the task can see it)

This pattern is used by a lot of drivers in embassy-stm32 to handle interrupts.