Tests for entity controllers

Started at #997254: [meta] Create tests that exercise CRUD & methods on all our entities.

There is some initial stuff on each entity testRead() provided at #1000862: Basic CRUD tests for entities.

This is focused on:

- Any $options that can be set for any kind of CRUD operation - so loading with the controllers or saving/deleting with the entities themselves - must be tested and verified to work as intended.
- We need to test $conditions on controllers. Not every possible condition, though; only each unique condition-handling logic path. Per controller. So we need just one check for all straight field filters (i.e., $query->condition($alias . $field_name, $value)), and then additional checks for any sort of condition that follows an alternate path.
- Tests should aggressively search for cache inconsistencies/misses, as the immaturity of VersioncontrolEntity::cacheGet generally makes me think we could see a fair number of those, and that's potentially really bad.