Android - tweaks to heartbeat collection subscription

[bplattenburg]

Today, we automatically subscribe any device using the hearbeat tool to the entire dittotools_devices collection, but that doesn't scale to production across multiple locations.

We either need to provide a way to disable this subscription (which has the downside of breaking multihop for a device which can't see the big peer e.g. lost LAN but still has BLE) or provide the ability to scope it to a more limited query like "devices at the same locationId as this device"

Note - we should also pair any limited query here with a matching eviction query to cover devices changing location and other edge cases