Unit Tests : Replace use of @Deprecated by @VisibleForTesting for methods/constructors/classes made public for Unit Testing only

@pmouawad ([Bug 63203](https://bz.apache.org/bugzilla//show_bug.cgi?id=63203&redirect=false)):
To discourage use of Default Constructors added for JUnit, we use @Deprecated.

But this is not very nice for quality auditing tools nor very readable.

This enhancement will introduce replacement of this by a new annotation extracted from under ASL2 license:

https://github.com/aosp-mirror/platform_frameworks_base/blob/8b2c3a14603d163d7564e6f60286995079687690/core/java/com/android/internal/annotations/VisibleForTesting.java

OS: All