Preparing for embedded-hal 1.0

[JohnAZoidberg]

I had a tough time with all these generic traits and structs. It compiles but I haven't tested it yet.
Must for merge wait until embedded-hal 1.0 is released and rp2040-hal is also with support for that.

[ithinuel]

I changed the target branch of the PR. Some of the changes (namely to the latest rp2040-hal) have already been integrated there.

[JohnAZoidberg]

Thank you, fixed up :)

[JohnAZoidberg]

Tested build with: cargo build --target=thumbv6m-none-eabi

[ithinuel]

I reviewed the current state of this crate and I have some doubts on what's the proper way to move forward with support for both embedded-hal 0.2.7 and 1.0-*

On the implementation side:

• the cortex-m crate implements delay for embedded-hal 0.2.4
• rp2040-hal implements various delay traits from embedded-hal 0.2.7 and 1.0-*

In theory, we should aim at supporting any delay source (provided they implement the HAL).
Moving the eh-1.0 now would deny support from at least cortex-m (until itself implements eh-1.0).

I also realized the CountDown support was broken, it should be as it is in: #27