refactor(libanki): migrate TestClass and rename TestClass to AnkiTest

[david-allison]

Most of libanki testing requires JvmTest

• JvmTest uses the AnkiTest interface
• RobolectricTest uses the AnkiTest interface

In order to move JvmTest out of AnkiDroid and into something libanki can use, we first need to move AnkiTest

AnkiTest must be usable by libanki/test and AnkiDroid/test, so define a new module: libanki:testutils to avoid a circular dependency, without exposing test-related classes to the non-test AnkiDroid.

Then, break up the dependencies, and move AnkiTest and a few dependencies to libanki:testutils

Fixes

• Part of Split libanki & tests into a separate module #18015
  • the module is created; tests are where we'll see huge speed improvements

How Has This Been Tested?

Unit test only
I haven't checked AndroidTest, will trust CI

Learning

This is not fun, but it's nearly over

Context Parameters would be useful architecturally, soon... 😆

Checklist

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[david-allison]

I'll split this out into smaller PRs, probably don't have maintainer effort for something this size

• refactor(libanki): begin removing AnkiDroid dependencies from TestClass  #18838
• refactor(libanki): continue removing AnkiDroid dependencies from TestClass  #18860
• refactor(libanki): add libanki:testutils #18862
• refactor(libanki): finish removing AnkiDroid dependencies from TestClass #18911