Bluetooth Low Energy Privacy (MAC randomisation)

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I want PineTime Bluetooth MAC address to change periodically.

Description

Bluetooth and Wi-Fi scanning is widely used by Apple and Google to improve location services as an alternative to GPS geolocation. This works on smartphones by periodically sending aforementioned companies a list of discoverable Wi-Fi SSIDs and Bluetooth MACs that are in scanning range. In practice, this means that while PineTime's Bluetooth MAC is static and there are any smartphones of non-privacy-conscious users (e.g. a fellow passenger on the bus) in range with the Bluetooth scanning enabled, it is trivial for Apple & Google (and whomever this information is sold to or shared with, legally or not) to build an extensive profile of such PineTime user’s movements.

The NimBLE stack supports Bluetooth LE privacy:

LE Privacy 1.2 for frequent changes to the device address to make it difficult to track for outsiders

I propose adding this important feature to protect PineTime users from global location tracking by third parties.

Start by reviewing the NimBLE documentation linked in the issue, focusing on its LE Privacy 1.2 support and how it applies to PineTime. The issue names no source files or tests, so locate the Bluetooth initialization and advertising entry points first. Done means the device periodically changes its Bluetooth address while remaining discoverable and usable.