MM-36764 mlog refactor (#18118)

Refactor mlog
- simplify mlog by removing redundant code
- remove Zap dependency
- update unit test helpers
- update logging config
- update auditing

services/imageproxy/local.go

@@ -46,12 +46,7 @@ func makeLocalBackend(proxy *ImageProxy) *LocalBackend {
 	impl := imageproxy.NewProxy(proxy.HTTPService.MakeTransport(false), nil)
 
 	if proxy.Logger != nil {
-		logger, err := proxy.Logger.StdLogAt(mlog.LevelDebug, mlog.String("image_proxy", "local"))
-		if err != nil {
-			mlog.Warn("Failed to initialize logger for image proxy", mlog.Err(err))
-		}
-
-		impl.Logger = logger
+		impl.Logger = proxy.Logger.With(mlog.String("image_proxy", "local")).StdLogger(mlog.LvlDebug)
 	}
 
 	baseURL, err := url.Parse(*proxy.ConfigService.Config().ServiceSettings.SiteURL)