Implement BLE Scanner

[dhalbert]

... or the equivalent, so that beacons can be detected.

[rdagger]

Looking forward to this feature. Do you think scanning will be implemented soon?

[dhalbert]

It will be after 4.0 is out. There are other BLE things to do, like BLE HID (which needs pairing/bonding), and we'll prioritize those after the 4.0 release.

[rdagger]

Sounds great! You guys are doing a fantastic job.

[blademckain]

+1 need ble scanner! :)

[dhalbert]

Implemented by #1993.

[rdagger]

That's great! Thanks.

[dhalbert]

This will be in 5.0.0-alpha.0, and is already available in the master builds here on S3: https://adafruit-circuit-python.s3.amazonaws.com/index.html?prefix=bin

[rdagger]

The scanning works! Here's my code:

import bleio
scanner = bleio.Scanner()
entries = scanner.scan(1)

I have a couple of requests.

1. Scan returns a lot of duplicate entries. Would it be possible to only return unique entries? Would this also speed up the scanning?
2. Address.address_bytes returns the address reversed. Can it please be swapped? On a side note, it looks like CircuitPython doesn't support reversing strings using [::-1]. It throws NotImplementedError only slices with step=1 (aka None) are supported.

Thanks again for all the great code.