Add device_tracker.bluetooth_update service (#15252)

* Add device_tracker.bluetooth_update service

Will immediately scan for Bluetooth devices outside of the interval timer. Allows for less frequent scanning, with scanning on demand via automation.

* remove excess whitespace per bot comments

* Refactored update_bluetooth to call new function update_bluetooth_once

* Change service name to bluetooth_tracker_update to reflect platform name

* Reformat for line length

* Linting fix, pydoc, first line should end with a period

* Fixed a method call, and removed some more unsused parameters