Use the nimble stack instead of current bluetooth stack

**Describe the problem you have/What new integration you would like**

The current bluetooth implementation uses the majority of available flash and memory space.
Someone has backported the new nimble stack to arduino (https://github.com/h2zero/NimBLE-Arduino), with only minor differences to the API.

It would be great if all the bluetooth classes could be ported to use this library instead of the current implementation.

**Please describe your use case for this integration and alternatives you've tried:**

**Additional context**

Start by reviewing the current Bluetooth implementation and the NimBLE-Arduino library linked in the request, then identify every Bluetooth class affected by the API differences. Done means all Bluetooth classes use the NimBLE stack while preserving existing behavior and reducing flash and memory usage; the issue names no files or tests.

Written by the indexing model from the issue text.