make versioning plugin more clearly a test-only thing

rename to test_versioning
set maturity to experimental

mysql-test/suite/versioning/common.opt

 --system-versioning-transaction-registry=1
---plugin-load=versioning
+--plugin-load-add=test_versioning

plugin/versioning/CMakeLists.txt

@@ -13,5 +13,5 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 
-MYSQL_ADD_PLUGIN(versioning versioning.cc RECOMPILE_FOR_EMBEDDED
-  MODULE_ONLY MODULE_OUTPUT_NAME "versioning" COMPONENT Test)
+MYSQL_ADD_PLUGIN(test_versioning versioning.cc RECOMPILE_FOR_EMBEDDED
+  MODULE_ONLY COMPONENT Test)

plugin/versioning/versioning.cc

@@ -189,7 +189,7 @@ maria_declare_plugin(versioning)
 {
   MYSQL_REPLICATION_PLUGIN, // initialized after MYSQL_STORAGE_ENGINE_PLUGIN
   &versioning_plugin,
-  "versioning",
+  "test_versioning",
   "MariaDB Corp",
   "System Vesioning testing features",
   PLUGIN_LICENSE_GPL,
@@ -199,6 +199,6 @@ maria_declare_plugin(versioning)
   NULL,                       /* status variables                */
   NULL,                       /* system variables                */
   "1.0",                      /* string version */
-  MariaDB_PLUGIN_MATURITY_STABLE /* maturity */
+  MariaDB_PLUGIN_MATURITY_EXPERIMENTAL
 }
 maria_declare_plugin_end;