This is the first version of the SR speedup feature for MariaDB 10.6.

Now all galera_sr tests succeed when SR speedup is disabled
and most galera_sr MTR tests succeed when SR speedup up is enabled.
The failing tests are listed in "skipped_tests" file.

The following MTR test suite run succeeds:

(cd mysql-test; ./mysql-test-run.pl --mysqld="--wsrep_SR_store=undolog"
                 --suite=galera_sr --skip-test-list=../skipped_tests --force)

include/wsrep/client_state.hpp

@@ -926,7 +926,16 @@ namespace wsrep
         {
             return transaction_;
         }
-
+#ifdef WITH_WSREP_SR_SPEEDUP
+        /**
+         * Return a reference to the transaction associated
+         * with the client state.
+         */
+        wsrep::transaction& transaction()
+        {
+            return transaction_;
+        }
+#endif /* WITH_WSREP_SR_SPEEDUP */
         const wsrep::ws_meta& toi_meta() const
         {
             return toi_meta_;