Hide connection quality indicators behind a developer setting

Calls are an environment with high cognitive load, so it's important that we keep extra UI elements like these to a minimum and stick to what's been explicitly designed. I assume that this was here as a developer feature to diagnose reliability of the back end components, which is perfectly fine, so I've kept it behind a developer setting rather than fully removing it.

src/settings/useSetting.ts

@@ -101,6 +101,9 @@ export const useOptInAnalytics = (): DisableableSetting<boolean | null> => {
 export const useDeveloperSettingsTab = () =>
   useSetting("developer-settings-tab", false);
 
+export const useShowConnectionStats = () =>
+  useSetting("show-connection-stats", false);
+
 export const useDefaultDevices = () =>
   useSetting("defaultDevices", {
     audioinput: "",