[Recorder] Feature request: activation interval for HR and GPS

Feature request for the recorder app: Can we set intervals for the heart rate and GPS which activate the sensors only occasionally?

At the moment, when the app records heart rate and GPS it seems that it turns these sensors on permanently. But these sensors drain the battery. And often it is not necessary to record these every few seconds.

If there was a setting, one could e.g. set the GPS to every 30 minutes and the heart rate to every 5 minutes, so these sensors are turned on at these intervals and turned off again as soon as they get a reliable value (usually after half a minute or a minute).

The database can still keep recording at much shorter intervals, but it would contain these values only when the sensor is active.

The widget could show the relevant sensors greyed out when they are not active and in colour when they are activated, similar to what the HRM Widget+ does.

Start by locating the recorder app's heart-rate and GPS sensor handling, the database recording path, and the widget display code. Trace how sensors are currently activated and how reliable readings are detected; done means configurable intervals, sensors switching off after valid readings, sparse database values, and grey/coloured widget states.

Written by the indexing model from the issue text.