Add a test that checks invisible objects are iterated over by the
`IO::AbstractHierarchyIterator` class, when a suitable depsgraph is given.
No functional changes.
And make them part of the blender_test runner. The one exception is blenlib
performance tests, which we don't want to run by default. They remain in their
own executable.
Differential Revision: https://developer.blender.org/D8498
