MM-22051: Remove ToJson from model (part 1) (#18005)

https://mattermost.atlassian.net/browse/MM-22051

```release-note
Removed the following methods/functions:
(ad *AccessData) ToJson()
(ar *AccessResponse) ToJson()
(ar *AnalyticsRow) ToJson()
(ar AnalyticsRows) ToJson()
(o *Audit) ToJson()
(o Audits) ToJson()
(ad *AuthData) ToJson()
(ar *AuthorizeRequest) ToJson()
(o *ChannelPatch) ToJson()
(o *ChannelsWithCount) ToJson()
(o *ChannelCounts) ToJson()
(o *ChannelData) ToJson()
(o *ChannelMembers) ToJson()
(o *ChannelUnread) ToJson()
(o *ChannelUnreadAt) ToJson()
(o *ChannelStats) ToJson()
(o *ChannelView) ToJson()
(o *ChannelViewResponse) ToJson()
(o *ClusterDiscovery) ToJson()
(ci *ClusterInfo) ToJson()
(cs *ClusterStats) ToJson()
(o *Command) ToJson()
CommandListToJson(l []*Command) string
(o *CommandArgs) ToJson()
(cmr *CommandMoveRequest) ToJson()
(o *CommandResponse) ToJson()
(c *Compliance) ToJson()
(c Compliances) ToJson()
(o *Config) ToJson()
EmojiListToJson(emojiList []*Emoji)
```

testlib/resources.go

@@ -4,6 +4,7 @@
 package testlib
 
 import (
+	"encoding/json"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -206,8 +207,13 @@ func setupConfig(configDir string) error {
 		return errors.Wrapf(err, "failed to create config directory %s", configDir)
 	}
 
+	buf, err := json.Marshal(config)
+	if err != nil {
+		return fmt.Errorf("failed to marshal config: %v", err)
+	}
+
 	configJSON := path.Join(configDir, "config.json")
-	err = ioutil.WriteFile(configJSON, []byte(config.ToJson()), 0644)
+	err = ioutil.WriteFile(configJSON, buf, 0644)
 	if err != nil {
 		return errors.Wrapf(err, "failed to write config to %s", configJSON)
 	}