Fixes androidx import, lint & powermock reflection issues

[oguzkocer]

This PR is a collection of minor fixes to get the project in a state where ./gradlew build is successful. This will help prepare the project for further updates such as Gradle/AGP upgrade, Buildkite integration and publishing to S3 support.

• cc62a7e fixes imports for Fragment & AppCompatActivity in PermissMeTests
• c1a89c3 fixes the MockClassLoader cannot access jdk/internal/reflect superclass error that happens in JDK 11. Admittedly I am not too familiar with powermock, but as I understand it, powermock is trying to access some internal files it shouldn't. There is an open issue about this with more details: Power mock is not working with JDK 9, Getting initializationError(PowermockTest): java.lang.reflect.InvocationTargetException powermock/powermock#901
• f862146 fixes a lint issue where getColumnIndex was resulting in Error: Value must be ≥ 0 [Range]

[obsantos]

Thanks for these changes. We will have to revisit the unit tests here because we have plans to move away from Powermock on the main repo, but we can definitely do that on future PRs