os.getenv() will use it (when available) to load variables from
/.env
This will also be useful when we need secrets or config for
CircuitPython outside of the VM (like WiFi credentials.)
Fixes#4212
also initializes in the same way where it takes from a true random
source when available through os.urandom(). After initializing, it
produces deterministic results until the seed is set.
This replaces urandom!
Fixes#139.
