* MM-21012: Revamp websocket implementation
We replace the old gorilla/websocket implementation with the
gobwas/ws library. The gorilla library was in maintenance mode
and had a high level API due to which we cannot use that for
situations where a large number of concurrent connections needs
to be supported.
The ws library is a very low-level library that allows us
to work with raw net.Conns. We make several improvements:
- We completely remove the reader goroutines, and instead
replace them with a manual epoll implementation which sends off
messages to be read when it receives any data on the connection.
This lets us scale to a much larger number of connections.
- The reader buffer is eliminated, because we directly read
from the connection now.
https://mattermost.atlassian.net/browse/MM-21012
```release-notes
Improved the websocket implementation by using epoll manually
to read from a websocket. As a result, the number of goroutines
is expected to go down by half.
```
* fix tests
* fix shadowing errors
* final changes
* windows support!
* Remove pointer to waitgroup
* Fix edge case
* Trigger CI
* Trigger CI
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
