Bluetooth and Bluetooth le scanner

[benroeder]

The pi4 has built in Bluetooth and Bluetooth LE.
Looking at the the number of bluetooth devices is a useful proxy for the number of people in range of the scanner, which can help with capacity planning and debugging.

I here is a working version
wifinigel/wiperf_poller#8

[benroeder]

Will create and export a dashboard and add as a pull request on this repo