GraphQL (part 1): Store layer (#19465)

We add the necessary store methods to use GraphQL

```release-note
NONE
```

manualtesting/manual_testing.go

@@ -178,7 +178,10 @@ func manualTest(c *web.Context, w http.ResponseWriter, r *http.Request) {
 
 func getChannelID(a app.AppIface, channelname string, teamid string, userid string) (string, bool) {
 	// Grab all the channels
-	channels, err := a.Srv().Store.Channel().GetChannels(teamid, userid, false, 0)
+	channels, err := a.Srv().Store.Channel().GetChannels(teamid, userid, &model.ChannelSearchOpts{
+		IncludeDeleted: false,
+		LastDeleteAt:   0,
+	})
 	if err != nil {
 		mlog.Debug("Unable to get channels")
 		return "", false