Passive beacon submission to beaconDB

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**Is your feature request related to a problem? Please describe.**
Google Play Services automatically submits nearby beacons to Google's database. A similar option in microG would help beaconDB greatly.

**Describe the solution you'd like**
An optional toggle under microG's location settings to passively (as in when other apps request location data) submit beacon data to the configured Ichnaea-compatible provider (which is beaconDB by default) would help beaconDB's dataset greatly.

Active beacon collecting has complex logic, taking movement and device-specific quirks into account but passive beacon collecting would be easier to implement.

**Describe alternatives you've considered**
A descriptive text under location settings, informing the user about beaconDB accepting submissions via beacon collector apps would be nice too.

**Additional context**
https://beacondb.net
https://support.google.com/maps/answer/1725632

Start by locating microG's location settings and the passive location-request path, then trace how the configured Ichnaea-compatible provider is used. Define the optional beacon submission toggle and its user-facing explanation, and verify that passive beacon data reaches the configured provider without requiring active collection.

Written by the indexing model from the issue text.