Exposure notifications: check for location permission broken

I originally observed the effects of this issue in Corona Contact Tracing Germany. In short, CCTG shows a "Exposure notifications disabled" warning while still collecting keys (https://codeberg.org/corona-contact-tracing-germany/cwa-android/issues/79). After further investigations, I also observed the reverse issue (no notification and not collecting keys) and came to the conclusion that the issue is in microG.
What's happening is the following:

• microG is using BLE scanning (correctly), which requires the permissions BLUETOOTH_ADMIN and one of ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION.
• microG does not check whether it was granted one of the location permissions, but instead it checks whether location services are enabled on the device, which is unrelated.
• As a result, microG shows a warning falsely if it has location permission but location services are disabled (approximately the issue I reported in CCTG), while still collecting keys. Perhaps more severe, it does not show a warning if it does not have location permission but location services are enabled.

Start by tracing microG's BLE scanning permission check and compare its use of granted location permissions with the device's location-services state. Reproduce both reported cases: warning with permission granted, and no warning without permission; done when the warning and key collection behavior reflect the actual required permission.