xo-gc: + CollectorTypeRegistry for streamlined init

utest/expression2_utest_main.cpp

@@ -1,6 +1,24 @@
 /* file expression2_utest_main.cpp */
 
-#define CATCH_CONFIG_MAIN
+#include <xo/subsys/Subsystem.hpp>
+
+#define CATCH_CONFIG_RUNNER
 #include "catch2/catch.hpp"
 
+int
+main(int argc, char* argv[])
+{
+    using xo::Subsystem;
+
+    // Your custom initialization code here
+    Subsystem::initialize_all();
+
+    // Run Catch2's test session
+    int result = Catch::Session().run(argc, argv);
+
+    // cleanup here, if any
+
+    return result;
+}
+
 /* end expression2_utest_main.cpp */