New RP2040/Raspberry Pi Pico USB Host MSC Demo

[rppicomidi]

Thank you @hathach for merging in the new host bulk endpoint support for RP2040. To try it out, I created a demo of Mass Storage Class integrated with FatFs and a Command Line Interpreter. It does not support CDC or HID like the demo code in examples directory. It supports up to 4 USB flash drives on a USB hub. The command line interpreter implements common commands like ls, rm, mkdir, cp, etc. If you want me to make it more generic to include as an example for tinyusb, please let me know and I will have a go at it.

[rppicomidi]

I have added new code here to allow you to run the
MSC demo using PIO USB.

[hathach]

Thank you, I am currently out of town til next week. Will check this out when backing at my desk. I have some local file system navigation written a while ago as well. We can combine them together.