refactor(plubin_libs): Add emqx_plugin_libs app

apps/emqx_plugin_libs/emqx_plugin_libs.app.src

@@ -0,0 +1,7 @@
+{application, emqx_plugin_libs,
+ [{description, "EMQ X Plugin utility libs"},
+  {vsn, "4.3.0"},
+  {modules, []},
+  {applications, [kernel,stdlib]},
+  {env, []}
+ ]}.

apps/emqx_plugin_libs/emqx_plugin_libs.erl

@@ -0,0 +1,18 @@
+%%--------------------------------------------------------------------
+%% Copyright (c) 2021 EMQ Technologies Co., Ltd. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%--------------------------------------------------------------------
+
+-module(emqx_plugin_libs).
+