refactor: change mria default rpc module from 'gen_rpc' to 'rpc'

Erlang distribution seems to outperform gen_rpc (unless gen_rpc clients
are scaled up, but this is not easy to achive for shard transport as it
may reorder events).

apps/emqx_conf/src/emqx_conf_schema.erl

@@ -652,7 +652,7 @@ fields("node") ->
                 hoconsc:enum([gen_rpc, rpc]),
                 #{
                     mapping => "mria.rlog_rpc_module",
-                    default => gen_rpc,
+                    default => rpc,
                     'readOnly' => true,
                     importance => ?IMPORTANCE_HIDDEN,
                     desc => ?DESC(db_rpc_module)

changes/ce/feat-11752.en.md

@@ -0,0 +1,3 @@
+Change default RPC driver from 'gen_rpc' to 'rpc' for core-replica database sync.
+
+This improves core-replica data replication latency.