Android Studio: generated test sources available to choose #692

Description

In Android Studio after first test generation generated test sources (build/generated) become available.
They are needed to be filtered out.

To Reproduce

Steps to reproduce the behavior:

Example:

1. Create new project in Android Studio
2. Add Android library
3. Use plugin to generate tests
4. Use plugin to generate tests again, you should see build/generated

Expected behavior

No generated test sources should appear.

Actual behavior

Generated test sources appear.

Visual proofs (screenshots, logs, images)

To be added.

Environment

Android Studio

Additional context

None