testutils: Drop virtTestResult

testutils: Drop virtTestResult

virtTestResult is suboptimal for a few reasons:

- It poorly duplicates virtTestRun pass/fail reporting logic
- It doesn't have virtTestRun's alloc testing support
- It only reports the test name _after_ the test has run.
- It doesn't follow the standard virtTestRun pattern that most other
  tests use.

There's no users left, so drop it. If any other async tests like eventtest
spring up that don't cleanly fit the virtTestRun pattern, I suggest they
just open code the support for it around virtTestRun