pw_unit_test: Support disabled tests

- As in Google Test, unit tests can be disabled by prefixing the test
  name or suite name with DISABLED_.
- Emit an event when a disabled test is encountered.
- Use a TestCase object inside of a TestInfo.

Change-Id: Ife5af89f959074f8034bc8cec14b88fbed720ffa
diff --git a/pw_unit_test/logging_event_handler.cc b/pw_unit_test/logging_event_handler.cc
index bf7ba22..bd063a2 100644
--- a/pw_unit_test/logging_event_handler.cc
+++ b/pw_unit_test/logging_event_handler.cc
@@ -76,4 +76,8 @@
          expectation.evaluated_expression);
 }
 
+void LoggingEventHandler::TestCaseDisabled(const TestCase& test) {
+  PW_LOG_DEBUG("Skipping disabled test %s.%s", test.suite_name, test.test_name);
+}
+
 }  // namespace pw::unit_test