Move some more atomic values under Channels (#18837)

* Move some more atomic values under Channels

The following fields were moved:

```
asymmetricSigningKey atomic.Value
clientConfig         atomic.Value
clientConfigHash     atomic.Value
limitedClientConfig  atomic.Value
```

And also moved the initialization order from NewServer
to Channels.Start to better reflect the order of things.

Removed AsymmetricSigningKey from ConfigService
as it was no longer used.

Removed calling regenerateClientConfig during startup explicitly
because it was anyways called from ensureAsymmetricSigningKey.

https://community-daily.mattermost.com/boards/workspace/zyoahc9uapdn3xdptac6jb69ic/285b80a3-257d-41f6-8cf4-ed80ca9d92e5/495cdb4d-c13a-4992-8eb9-80cfee2819a4?c=87df1e15-588e-49ff-8bd1-ffa9651b8c82
```release-note
NONE
```

* Fix lint error

```release-note
NONE
```

app/server.go

@@ -150,11 +150,6 @@ type Server struct {
 	pluginCommands     []*PluginCommand
 	pluginCommandsLock sync.RWMutex
 
-	asymmetricSigningKey atomic.Value
-	clientConfig         atomic.Value
-	clientConfigHash     atomic.Value
-	limitedClientConfig  atomic.Value
-
 	telemetryService *telemetry.TelemetryService
 	userService      *users.UserService
 	teamService      *teams.TeamService
@@ -447,17 +442,19 @@ func NewServer(options ...Option) (*Server, error) {
 	}
 
 	s.configListenerId = s.AddConfigListener(func(_, _ *model.Config) {
-		s.configOrLicenseListener()
+		ch := s.Channels()
+		ch.regenerateClientConfig()
 
 		message := model.NewWebSocketEvent(model.WebsocketEventConfigChanged, "", "", "", nil)
 
-		message.Add("config", s.ClientConfigWithComputed())
+		appInstance := New(ServerConnector(ch))
+		message.Add("config", appInstance.ClientConfigWithComputed())
 		s.Go(func() {
 			s.Publish(message)
 		})
 	})
 	s.licenseListenerId = s.AddLicenseListener(func(oldLicense, newLicense *model.License) {
-		s.configOrLicenseListener()
+		s.Channels().regenerateClientConfig()
 
 		message := model.NewWebSocketEvent(model.WebsocketEventLicenseChanged, "", "", "", nil)
 		message.Add("license", s.GetSanitizedClientLicense())
@@ -503,10 +500,6 @@ func NewServer(options ...Option) (*Server, error) {
 		s.Cluster.StartInterNodeCommunication()
 	}
 
-	if err = s.ensureAsymmetricSigningKey(); err != nil {
-		return nil, errors.Wrapf(err, "unable to ensure asymmetric signing key")
-	}
-
 	if err = s.ensurePostActionCookieSecret(); err != nil {
 		return nil, errors.Wrapf(err, "unable to ensure PostAction cookie secret")
 	}
@@ -519,8 +512,6 @@ func NewServer(options ...Option) (*Server, error) {
 		return nil, errors.Wrapf(err, "unable to ensure first run timestamp")
 	}
 
-	s.regenerateClientConfig()
-
 	subpath, err := utils.GetSubpathFromConfig(s.Config())
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to parse SiteURL subpath")
@@ -1914,12 +1905,8 @@ func (s *Server) ClusterHealthScore() int {
 	return s.Cluster.HealthScore()
 }
 
-func (s *Server) configOrLicenseListener() {
-	s.regenerateClientConfig()
-}
-
-func (s *Server) ClientConfigHash() string {
-	return s.clientConfigHash.Load().(string)
+func (ch *Channels) ClientConfigHash() string {
+	return ch.clientConfigHash.Load().(string)
 }
 
 func (s *Server) initJobs() {