[android] #6083 - add circle example

[tobrun]

Refs #6083,
add circle example
Review @ivovandongen

[mention-bot]

@tobrun, thanks for your PR! By analyzing this pull request, we identified @bleege and @zugaldia to be potential reviewers.

[tobrun]

In this PR i'm adding a new feature activity to the test application. This activity is automatically picked up by our auto sanity test generation tool and now fails in firebase test lab with the following exception:

This happens since the sanity test will wait for OnMapReadyCallback to be called. This is validated by the test by checking if mapboxMap instance in your Activity is filled up. In this PR I didn't add an mapboxMap class member to CircleLayer. After adding that the test will pass.

cc @mapbox/android

[ivovandongen]

LGTM. Little documentation on the Activity class wouldn't be out of place though:

mapbox-gl-native/platform/android/MapboxGLAndroidSDKTestApp/src/main/java/com/mapbox/mapboxsdk/testapp/activity/style/CircleLayerActivity.java

Line 31 in 0d92f72

public class CircleLayerActivity extends AppCompatActivity {

[zugaldia]

This is the new activity, looking good @tobrun :

[ivovandongen]

@tobrun Thanks for adding the documentation!

[tobrun]

cc @mapbox/android