update monitor client's memory and evict correctly (redis#12420)

A bug introduced in redis#11657 (7.2 RC1), causes client-eviction (redis#8687)
and INFO to have inaccurate memory usage metrics of MONITOR clients.

Because the type in `c->type` and the type in `getClientType()` are confusing
(in the later, `CLIENT_TYPE_NORMAL` not `CLIENT_TYPE_SLAVE`), the comment
we wrote in `updateClientMemUsageAndBucket` was wrong, and in fact that function
didn't skip monitor clients.
And since it doesn't skip monitor clients, it was wrong to delete the call for it from
`replicationFeedMonitors` (it wasn't a NOP).
That deletion could mean that the monitor client memory usage is not always up to
date (updated less frequently, but still a candidate for client eviction).

src/networking.c

@@ -3808,7 +3808,7 @@ size_t getClientMemoryUsage(client *c, size_t *output_buffer_mem_usage) {
  * classes of clients.
  *
  * The function will return one of the following:
- * CLIENT_TYPE_NORMAL -> Normal client
+ * CLIENT_TYPE_NORMAL -> Normal client, including MONITOR
  * CLIENT_TYPE_SLAVE  -> Slave
  * CLIENT_TYPE_PUBSUB -> Client subscribed to Pub/Sub channels
  * CLIENT_TYPE_MASTER -> The client representing our replication master.

src/replication.c

@@ -610,6 +610,7 @@ void replicationFeedMonitors(client *c, list *monitors, int dictid, robj **argv,
     while((ln = listNext(&li))) {
         client *monitor = ln->value;
         addReply(monitor,cmdobj);
+        updateClientMemUsageAndBucket(monitor);
     }
     decrRefCount(cmdobj);
 }

src/server.c

@@ -917,11 +917,9 @@ void removeClientFromMemUsageBucket(client *c, int allow_eviction) {
  * together clients consuming about the same amount of memory and can quickly
  * free them in case we reach maxmemory-clients (client eviction).
  *
- * Note: This function filters clients of type monitor, master or replica regardless
+ * Note: This function filters clients of type no-evict, master or replica regardless
  * of whether the eviction is enabled or not, so the memory usage we get from these
- * types of clients via the INFO command may be out of date. If someday we wanna
- * improve that to make monitors' memory usage more accurate, we need to re-add this
- * function call to `replicationFeedMonitors()`.
+ * types of clients via the INFO command may be out of date.
  *
  * returns 1 if client eviction for this client is allowed, 0 otherwise.
  */