Enquiring location service is used on Android

## 💬 Questions and Help
As the geolocator's document mentions, LocationManager will be used when the FusedLocationProviderClient is not available on Android. I have multiple android phones with different models and trying to use the flutter-geolocator package to collect accurate GPS reading. Some models can provide relatively acceptable readings, but some models have returned inaccurate results (some readings fly over more than 1km).

Could the inaccurate readings be provided by the LocationManager instead of FusedLocationProviderClient?Can we enquire which service is applied during the runtime of the app?

Update:
I am using `geolocator: ^6.2.1` for my application.

Start by reading the Android geolocator documentation and the provider-selection behavior involving FusedLocationProviderClient and LocationManager. Trace where the Android location provider is selected at runtime, then determine how the active service could be exposed or reported. Done means the selected provider can be identified reliably and the behavior is covered by appropriate documentation or tests.

Written by the indexing model from the issue text.