refactor(libanki): add libanki:testutils

[david-allison]

I split this out from #18813 to make it an easier review

• refactor(libanki): migrate TestClass and rename TestClass to AnkiTest #18813

---

• test modules can't depend on each other
• We need libanki specific test utilities in both:
  • libanki/test
  • AnkiDroid/test

These utilities are mostly:

• TestClass: a unit test with access to the Anki Collection
  • And a number of instance methods (soon to be extension methods)
• A TestClass will have a TestCollectionManager, which is the first interface which we extract in this PR
  • This allows a 'near-pure JVM' instance in libanki using an in-memory collection
  • A standard CollectionManager will be available, if the disk is required

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

[mikehardy]

okay

[Arthur-Milchior]

I'd just like some javadoc on the new interface. Even it only is @see CollectionManager.methodName so that android studio can show useful documentation.

In particular, i must admit i've little intuition of what you'd do with the backend method

Once documented fell free to merge

[david-allison]

@Arthur-Milchior As this is in a module which does not depend on AnkiDroid, we don't have a reference to CollectionManager, I've tweaked & copied the documentation instead.

• I removed getColUnsafe: not used in TestClass itself
• I removed setTestDispatcher and instead implemented it in JvmTest/RobolectricTest
• discardBackend was documented