[show][muxcable] add some new commands health, reset-cause, queue_info support for muxcable

[vdahiya12]

raising this because cherry-pick failed for 202012
master branch PR #2414

This PR adds the support for adding some utility commands for muxacble This includes commands for health, operationtime, queueinfo, resetcause

vdahiya@sonic:~$ show mux health Ethernet4
PORT          ATTR               HEALTH
---------     ---------------   --------
Ethernet4     health_check       Ok
vdahiya@sonic:~$ show mux health Ethernet4 --json
{
    "health_check": "Ok"
}

vdahiya@sonic:~$ show mux operation Ethernet4 --json {
    "operation_time": "22:22"
}
vdahiya@sonic:~$ show mux operation Ethernet4
PORT       ATTR              OPERATION_TIME
---------  --------------  ----------------
Ethernet4  operation_time                 22:22
vdahiya@sonic:~$

vdahiya@sonic:~$ show mux resetcause Ethernet4
PORT       ATTR           RESETCAUSE
---------  -----------  ------------
Ethernet4  reset_cause             0

vdahiya@sonic:~$ show mux resetcause Ethernet4 --json {
    "reset_cause": "0"
}

vdahiya@sonic:~$ show mux queueinfo Ethernet4 --json {
    "Remote": "{'VSC': {'r_ptr': 0, 'w_ptr': 0, 'total_count': 0, 'free_count': 0, 'buff_addr': 0, 'node_size': 0}, 'UART1': {'r_ptr': 0, 'w_ptr': 0, 'total_count': 0, 'free_count': 0, 'buff_addr': 209870, 'node_size': 1682183}, 'UART2': {'r_ptr': 13262, 'w_ptr': 3, 'total_count': 0, 'free_count': 0, 'buff_addr': 12, 'node_size': 0}}",
    "Local": "{'VSC': {'r_ptr': 0, 'w_ptr': 0, 'total_count': 0, 'free_count': 0, 'buff_addr': 0, 'node_size': 0}, 'UART1': {'r_ptr': 0, 'w_ptr': 0, 'total_count': 0, 'free_count': 0, 'buff_addr': 209870, 'node_size': 1682183}, 'UART2': {'r_ptr': 13262, 'w_ptr': 3, 'total_count': 0, 'free_count': 0, 'buff_addr': 12, 'node_size': 0}}"
}

What I did

How I did it

How to verify it

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)

[zjswhhh]

lgtm.