Add client info traffic stat fields. (#45)

Corresponding doc PR to valkey-io/valkey#327.

* `tot-net-in`: Total network input bytes read from this client. Added
in Valkey 8.0
* `tot-net-out`: Total network output bytes sent to this client. Added
in Valkey 8.0
* `tot-cmds`: Total count of commands this client executed. Added in
Valkey 8.0

---------

Signed-off-by: Chen Tianjie <TJ_Chen@outlook.com>

commands/client-list.md

@@ -36,6 +36,9 @@ Here is the meaning of the fields:
 * `resp`: client RESP protocol version.
 * `lib-name`: The client library name as set by `CLIENT SETINFO`
 * `lib-version`: The client library version as set by `CLIENT SETINFO`
+* `tot-net-in`: Total network input bytes read from this client. Added in Valkey 8.0
+* `tot-net-out`: Total network output bytes sent to this client. Added in Valkey 8.0
+* `tot-cmds`: Total count of commands this client executed. Added in Valkey 8.0
 
 The client flags can be a combination of: