Enable log messages in tracing with IREE_TRACING_MODE = 1. (#3602)

This matches what I wrote in the documentation... oops.
diff --git a/iree/base/tracing.h b/iree/base/tracing.h
index 98db68e..195d5c2 100644
--- a/iree/base/tracing.h
+++ b/iree/base/tracing.h
@@ -105,7 +105,8 @@
 // IREE_TRACING_MODE = 4: same as 3 with callstacks for all instrumentation
 #if !defined(IREE_TRACING_FEATURES)
 #if defined(IREE_TRACING_MODE) && IREE_TRACING_MODE == 1
-#define IREE_TRACING_FEATURES (IREE_TRACING_FEATURE_INSTRUMENTATION)
+#define IREE_TRACING_FEATURES \
+  (IREE_TRACING_FEATURE_INSTRUMENTATION | IREE_TRACING_FEATURE_LOG_MESSAGES)
 #undef IREE_TRACING_MAX_CALLSTACK_DEPTH
 #define IREE_TRACING_MAX_CALLSTACK_DEPTH 0
 #elif defined(IREE_TRACING_MODE) && IREE_TRACING_MODE == 2