In addition to the existing release test builds, we now also do a debug build with asan/ubsan and run tests with sanitizers.

This one caught a couple of memory leaks in test harnesses that I need to troubleshoot (the leak appears to be in the harness, not the scopehal blocks bein tested).

We still need a ton more tests to be written, of course. But that's orthogonal to the work on the test harness and infrastructure