[Xbee] Driver Rework & GUI to perform antenna test

Reworked Xbee driver to solve two criticalities:

• The Xbee couldn't share the SPI bus with other devices
• The driver was creating an unnecessary thread

TODO:

• Implement driver
• Write unit tests
• Handle Xbee status messages
• Update the XbeeStatus struct
• Test the driver on a real Xbee device
• Write tests for measuring packet loss & data rate
• Improve comments
• Improve unit tests (add edge cases)
• Add GUI for on-site antenna tests