Add Pico RP2040 (non-mbed) support

[adisbladis]

This adds support for RP2040 based boards such as the Pico and the Pico W using arduino-pico.
Note that this is distinctly different from the mbed-OS based platform which would have to be implemented separately.

I have tested this on a Pico W.

Github Actions related changes haven't been tested, only actually running the code on my board.

[adisbladis]

Ping @fabianoriccardi

[fabianoriccardi]

I will test it the next week with the Pico, however I see that some examples don't compile!

[adisbladis]

It's very hard to test CI locally because the Github Actions yml files don't exactly correspond to a set of commands that I can run.
The examples compile just fine, it's just hard to figure out the exact set of platform/url/board strings appease the CI.

[fabianoriccardi]

Did you tested RPI Pico with PlatformIO?

[adisbladis]

Did you tested RPI Pico with PlatformIO?

Yes. My primary use case for this is my espresso machine where I use platformio to build.

[fabianoriccardi]

The same issue appears with your project. Here I have opened the issue.

[fabianoriccardi]

May I add your name in license of hw_timer_pico.cpp/h files?

[adisbladis]

May I add your name in license of hw_timer_pico.cpp/h files?

Feel free.

[fabianoriccardi]

I prefer to insert a real name but you don't use it on GitHub...

[adisbladis]

My real name is Adam Hoese.