Moving mlog to corelibs (#16915)

* Moving mlog to corelibs

* Regenerating app layers

* Fix golangci-lint problem

* Fixing golangci-lint errors

* Renaming from corelibs to shared

* Renaming from corelibs to shared

* Fixing import

* Fixing merge problems

* Fixing build

shared/mlog/errors.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package mlog
+
+import (
+	"github.com/mattermost/logr"
+)
+
+// onLoggerError is called when the logging system encounters an error,
+// such as a target not able to write records. The targets will keep trying
+// however the error will be logged with a dedicated level that can be output
+// to a safe/always available target for monitoring or alerting.
+func onLoggerError(err error) {
+	Log(LvlLogError, "advanced logging error", Err(err))
+}
+
+// onQueueFull is called when the main logger queue is full, indicating the
+// volume and frequency of log record creation is too high for the queue size
+// and/or the target latencies.
+func onQueueFull(rec *logr.LogRec, maxQueueSize int) bool {
+	Log(LvlLogError, "main queue full, dropping record", Any("rec", rec))
+	return true // drop record
+}
+
+// onTargetQueueFull is called when the main logger queue is full, indicating the
+// volume and frequency of log record creation is too high for the target's queue size
+// and/or the target latency.
+func onTargetQueueFull(target logr.Target, rec *logr.LogRec, maxQueueSize int) bool {
+	Log(LvlLogError, "target queue full, dropping record", String("target", ""), Any("rec", rec))
+	return true // drop record
+}