test: rework lib stuff to share common files

test/lib/emitter/plugin/plugin.cpp

@@ -0,0 +1,19 @@
+#include <cr.h>
+#include "types.h"
+
+CR_EXPORT int cr_main(cr_plugin *ctx, cr_op operation) {
+    switch(operation) {
+    case CR_STEP:
+        static_cast<test_emitter *>(ctx->userdata)->publish(event{});
+        static_cast<test_emitter *>(ctx->userdata)->publish(message{42});
+        static_cast<test_emitter *>(ctx->userdata)->publish(message{3});
+        break;
+    case CR_CLOSE:
+    case CR_LOAD:
+    case CR_UNLOAD:
+        // nothing to do here, this is only a test.
+        break;
+    }
+
+    return 0;
+}