Expand unit test for `BKE_fcurve_active_keyframe_index()` to test edge
cases better.
This also introduces a new test macro `EXPECT_BLI_ASSERT()`, which can be
used to test that an assertion fails successfully.
No functional changes to actual Blender code.
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
