* feat(emqx_conf): move conf manager for emqx_machine to emqx_conf
* chore(emqx_conf): change emqx:get_config/2 to emqx_conf:get/2
* fix: common test failed
* fix: badmatch by typo wrong key
* fix(emqx_conf): get the wrong core nodes
* fix(emqx_conf): get core node's tnx_id not latest tnx_id
* fix: add ro_transation when copy conf file
* fix: delete debug info
* fix: change ekka_rlog to mria_rlog
* fix: remove cluster_rpc from emqx_machine.
* fix: don't call ekka:start/0 explicitly
* fix: ekka should be start in emqx_machine
* fix(emqx_machine): Fix start/stop callbacks
* chore(ekka): Bump version to 0.11.1
* fix(router): Wait for the tables
* fix(emqx_cluster_rpc): Stop cluster RPC when joining a cluster
* fix(emqx_app): Fix a deadlock when joining the cluster
* fix(emqx_telemetry): Wait for mnesia tables
* test(ct_helper): Start ekka before emqx
prior to this cahnge emqx node shutdown is done by init:stop
which might have undesired stop order of the applications
in this change, emqx_machine_terminator is added to stop apps
in defined order and then terminate the node in infinite loop