* MM-29980: Optimize profilesInChannels cache to fast path
We add one more message type to the fast path- profiles in channels. There
are 2 primary reasons for this:
- This is not really a new model type, but just a map of users. And users already use
the fast path. So we can get some more gains without really investing much more code.
- A more important reason is that with the upcoming striped mutex changes, we will get
a higher throughput at the cost of a bit more CPU utilization. The reason being that
since less amount of time will be spent in lock-contention, the CPU is free to do more
stuff. So this change is to counter that increase.
As usual, this gives much better performance than the original decoder.
Micro-benchmark results
```
name old time/op new time/op delta
LRU/UserMap=new-8 16.6µs ± 3% 3.9µs ± 4% -76.15% (p=0.000 n=10+10)
name old alloc/op new alloc/op delta
LRU/UserMap=new-8 4.78kB ± 0% 2.74kB ± 0% -42.65% (p=0.000 n=10+10)
name old allocs/op new allocs/op delta
LRU/UserMap=new-8 38.0 ± 0% 30.0 ± 0% -21.05% (p=0.000 n=10+10)
```
https://mattermost.atlassian.net/browse/MM-29980
Here are some results from a load test. The comparison is done with a 2 node cluster; one running master
and one running with this patch so that it's easier to compare. The total users are 2000.
<See PR>
```release-note
NONE
```
* Fix gofmt
* Trigger CI
