Unignore tests that should run on Robolectric

**Is your feature request related to a problem? Please describe.**
In https://github.com/googlemaps/android-maps-utils/pull/649 we changed from using an emulator on Travis to using Robolectric CI, which means that all instrumented tests that were previously in the `androidTest` folder got moved to the `test` folder so they run on the JVM instead of an Android device or emulator.

In the first implementation of Robolectric in https://github.com/googlemaps/android-maps-utils/pull/649, we had to ignore some tests that failed on Robolectric - these are all currently annotated with `@Ignore`.

**Describe the solution you'd like**
We should try and get the ignored tests running on Robolectric.

Here are tests that we should try to get running first, which previously ran on the emulator on Travis:
* `KmlContainerParserTest ` - entire class

These tests would be nice-to-have, although they were already skipped on the emulator on Travis because of existing issues:
* `GeoJsonPointStyleTest.testIcon()`
* `KmlStyleTest.testMarkerColorLeadingSpace()`
* `KmlStyleTest.testMarkerColorTrailingSpace()`

**Describe alternatives you've considered**
* Do nothing - continue to ignore the tests
* Try out Firebase Test Lab - https://firebase.google.com/docs/test-lab

**Additional context**
https://github.com/googlemaps/android-maps-utils/pull/649 contains some notes in the comments for issues I ran into when implementing Robolectric.

https://github.com/googlemaps/android-maps-utils/pull/573 contains some notes on why the nice-to-have tests were failing on the emulator on Travis.