AndroidX Test java package names should match their maven artifact names

Currently there is a bunch of AndroidX Test classes whose namespace does not match their maven name

Separate artifacts could be created for these classes:
androidx.test.filters
androidx.test.platform
androidx.test.annotation

There is also a bunch of existing androidx.test.runner classes that are actually in the androidx.test:monitor artifact. Those might be more complicated to clear up...

Start by inspecting the Maven artifact layout and the classes in the named androidx.test.filters, androidx.test.platform, androidx.test.annotation, and androidx.test.runner namespaces. Determine which packages should have separate artifacts and how the existing runner classes relate to the monitor artifact; done means an agreed, consistent package-to-artifact plan, including the noted runner cases.

Written by the indexing model from the issue text.