MM-11029 Adding plugin logging functionality. (#9034)

* Capturing stdout, stderr of plugins in logs.

* Cleanup go-plugin debug logs.

* Adding logging to plugin API

* Generating mocks.

* godoc convention

mlog/sugar.go

@@ -0,0 +1,28 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package mlog
+
+import "go.uber.org/zap"
+
+// Made for the plugin interface, use the regular logger for other uses
+type SugarLogger struct {
+	wrappedLogger *Logger
+	zapSugar      *zap.SugaredLogger
+}
+
+func (l *SugarLogger) Debug(msg string, keyValuePairs ...interface{}) {
+	l.zapSugar.Debugw(msg, keyValuePairs...)
+}
+
+func (l *SugarLogger) Info(msg string, keyValuePairs ...interface{}) {
+	l.zapSugar.Infow(msg, keyValuePairs...)
+}
+
+func (l *SugarLogger) Error(msg string, keyValuePairs ...interface{}) {
+	l.zapSugar.Errorw(msg, keyValuePairs...)
+}
+
+func (l *SugarLogger) Warn(msg string, keyValuePairs ...interface{}) {
+	l.zapSugar.Warnw(msg, keyValuePairs...)
+}