Sessions must not enqueue messages when another process is taking over
the client id, since it already passed on the message queue in the
session state.
Without this fix, messages arriving after `{takeover, 'begin'} to a
channel with no connection (i.e., a persistent session) would be lost.
(Same as #6289 )
This adds the information from `proc_lib:initial_call/1` and the
current stacktrace from the process info to `emqx_sys_mon:procinfo/1`
to aid in debugging some warnings with no context such as the
following:
```
2021-11-23T12:33:59.387818+00:00 [warning] info: [{old_heap_block_size,45988046},{heap_block_size,22177879},{mbuf_size,0},{stack_size,40},{old_heap_size,22354134},{heap_size,7106339}], line: 130, mfa: emqx_sys_mon:handle_info/2, msg: large_heap, procinfo: [{pid,<0.2667.0>},{memory,579763664},{total_heap_size,68510672},{heap_size,22177879},{stack_size,40},{min_heap_size,233},{initial_call,{proc_lib,init_p,5}},{current_function,{gen,do_call,4}},{registered_name,[]},{status,running},{message_queue_len,360945},{group_leader,<0.1660.0>},{priority,normal},{trap_exit,false},{reductions,16493271},{last_calls,false},{catchlevel,4},{trace,0},{suspending,[]},{sequential_trace_token,[]},{error_handler,error_handler}]
```
Prior to this fix, 'kick' and 'discard' calls may timeout (or
fail for other reason), failures lead to only a log, then
continue to allow the new session to get registered.
As a result, in case a client is stuck, there is no way to
force it to step down, end up with multiple connections (sessions)
for the client ID in dashboard.
After this fix, the stale pids are notified to shutdown
via a gen_server:call, and forced with a exit(Pid, kill) for any
exception happend to the gen_server:call
app 4.3.9 was release as a part of enterprise e4.3.4
but opensource v4.3.9 is not releasd yet, but we have
to bump app version to 4.3.10 to make appup work for the next
release (either opensource or enterprise).
Application:stop is call after the root supervisor is stopped,
in our case, prior to this fix, emqx_sup is stopped before
the listeners (hence the emqx_connection processes).
This causes shutdown to emit a lot of error logs
e.g. emqx_broker pool is down, but emqx_connection process is still
trying to call the pool
