Generic serial communication over smart ports.

[Tropix126]

What's the motivation for this feature?

Smart ports in PROS support being used as generic serial ports (through serctl and fopen).

Describe the solution you'd like

Support generic serial functionality on smart ports through pros-rs. Can look at past work such as https://github.com/serialport/serialport-rs for inspiration in the API or use something similar to the VEXLink I/O API. vex_rt also has an API for this if we want to look at that too.

Additional context

https://pros.cs.purdue.edu/v5/tutorials/topical/filesystem.html?highlight=serial