Add mobile metrics (#27045)

* Add mobile metrics

* Fix mocks

* Add tests

* Fix lint

* Address feedback

* Fix lint

* Fix test

* Fix CI

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Co-authored-by: Mattermost Build <build@mattermost.com>

server/einterfaces/metrics.go

@@ -114,4 +114,7 @@ type MetricsInterface interface {
 	ObserveClientTeamSwitchDuration(platform, agent string, elapsed float64)
 	ObserveClientRHSLoadDuration(platform, agent string, elapsed float64)
 	ObserveGlobalThreadsLoadDuration(platform, agent string, elapsed float64)
+	ObserveMobileClientLoadDuration(platform string, elapsed float64)
+	ObserveMobileClientChannelSwitchDuration(platform string, elapsed float64)
+	ObserveMobileClientTeamSwitchDuration(platform string, elapsed float64)
 }