perf: use erpc multicall in ekka_locker

[terry-xiaoyu]

rpc:multicall/5 has a performance issue when called by many processes in parallel.

To reproduce the problem:

Setup a 2-node emqx 4.4.35 cluster, on each node spawn a lot of processes (50K in my example) that call rpc:multicall/5 in a loop:

(fun() ->
    N = 50_000,
    Nodes = ekka_mnesia:running_nodes(),
    _ = [
    spawn_link(fun() ->
      (fun Loop(I) ->
          rpc:multicall(Nodes, erlang, system_time, [], 30000),
          receive
             q -> ok;
             Msg when I =< 0 ->
                io:format("----received ~p~n", [Msg]),
                ok;
             Msg ->
                io:format("----received ~p~n", [Msg]),
                Loop(I - 1)
          after
             1000 ->
                if I =< 0 -> ok;
                   true -> Loop(I - 1)
                end
          end
        end)(30)
    end) || _ <- lists:seq(1, N)]
end)().

I don't know if this problem also exists on newer OTP versions than OTP 24.3.4.17-2.

[zmstone]

maybe add description