ulib/test-exceptions

This library provides utilities to handle exceptions in unittests. Expected exceptions can be registered which will catch and handle them appropriately, whereas unexpected exceptions or failing to catch a registered exception will trigger a test failure.

This is a replacement for ulib/unittest's RUN_TEST_ENABLE_CRASH_HANDLER mechanism, the differences being:

• C++ object instead of macros
• synchronous behavior for simplicity and predictability
• not dependent on any particular test library so can be used equally well with unittest or zxtest
• uses new channel-based exception APIs