Add picolibc as an alternative of newlib?

[jacky-lau-1]

Picolibc is a C library designed for embedded 32 and 64 bit systems with limited ROM and RAM. And it has been tested on RISC-V and ARM processors. You can read the introduction here: https://keithp.com/picolibc/picolibc-2021-notes.pdf

[cmuellner]

We support this.
Pull request exists here: #1119

Feel free to finish that up:

• ensure that only upstream components are required
• ensure that tests can be executed
• create an ignorelist if you encounter valid reasons for failing tests