Improved Raspberry Pi Pico support

[LinuxJedi]

Fixes and improvements for RP2040 and added RP2350 support:

• Made UART printf output optional
• Made WiFi support optional
• Added compile support for RP2350
• Re-wrote README
• Fixed compile issues

Requires wolfSSL/wolfssl#8153

[LinuxJedi]

Addressed comments indicated in a Slack conversation.

[dgarske]

Cannot get past this error with the blink:

[ 41%] Built target benchmark
[ 41%] Building C object CMakeFiles/Wifi.dir/src/blink.c.obj
/home/davidgarske/GitHub/wolfssl-examples/RPi-Pico/src/blink.c:23:10: fatal error: pico/cyw43_arch.h: No such file or directory
   23 | #include "pico/cyw43_arch.h"
      |          ^~~~~~~~~~~~~~~~~~~
compilation terminated.
make[2]: *** [CMakeFiles/Wifi.dir/build.make:76: CMakeFiles/Wifi.dir/src/blink.c.obj] Error 1
make[1]: *** [CMakeFiles/Makefile2:1840: CMakeFiles/Wifi.dir/all] Error 2
make: *** [Makefile:91: all] Error 2

[LinuxJedi]

OK, lots of improvements in this morning's update:

• Added the compile fixes we discussed
• Fixed the issue you had with WiFi compiling (see below)
• Added WiFi setup options to README and descriptions in CMake
• Added a prerequisites section
• Added a section for uploading to the Pico
• Added a section for terminal output
• Specified that you can use any PICO_BOARD and pointed to the list

WiFi compiling issues

So, USE_WIFI was on by default, but unless PICO_BOARD was set to a board that had a CYW43 chip, the include directories / linking were not setup for WiFi. Now:

• USE_WIFI is now off by default
• If you try to use USE_WIFI without a PICO_BOARD that has a CYW43, CMake will error with "You can only set USE_WIFI when a PICO_BOARD with wifi is used"

[LinuxJedi]

Another push because I quickly added RISC-V mode for the RP2350 too.

[dgarske]

Worked amazing!
wolfCrypt test/bench both run and pass.
Tested on MacOS with Intel and Rpi5.
Ran on RP2040
Thank you