Switch to CAN_FD on the Teensy's and Pi

[Levi-Lesches]

A CAN frame can only fit 8 bytes of data, which is extremely limiting. Using a complex function we were able to carefully bring down some floats to 2 bytes. But a much simpler implementation would need 4 bytes for an accuracy of <0.01. With this implementation, we can only fit 2 floats per frame, resulting in many more frames needing to be sent.

A CAN_FD frame can contain 64 bytes of data, raising our data cap from 2 floats to 16, which should solve our issues. We've had compatibility issues getting CAN_FD to work on the Teensy boards and the Pi, so let's take this slow and work on a separate branch:

1. Convert the CAN library to CAN_FD and test on a Teensy (this issue)
2. Convert the Pi code to CAN_FD and test Switch to CAN_FD Subsystems-Computer#7

When both work, we can switch.

[Levi-Lesches]

Update:

• Raspberry Pi is currently using an MCP2510 chip, we need the MCP2518fd chip
• All Teensy boards need to use CAN3