[MM-13833] Configured unit tests to log through t.Log (#10272)

* Rerouted the unit test logs through t.Log

* resolving merge confilvts

* Update testing.go

* Update helper_test.go

* Added godocs for NewTestingLogger

* Added go docs for NewTestingLogger

* Resolving conflicts

mlog/testing.go

@@ -0,0 +1,42 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package mlog
+
+import (
+	"strings"
+	"testing"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+)
+
+// testingWriter is an io.Writer that writes through t.Log
+type testingWriter struct {
+	tb testing.TB
+}
+
+func (tw *testingWriter) Write(b []byte) (int, error) {
+	tw.tb.Log(strings.TrimSpace(string(b)))
+	return len(b), nil
+}
+
+// NewTestingLogger creates a Logger that proxies logs through a testing interface.
+// This allows tests that spin up App instances to avoid spewing logs unless the test fails or -verbose is specified.
+func NewTestingLogger(tb testing.TB) *Logger {
+	logWriter := &testingWriter{tb}
+	logWriterSync := zapcore.AddSync(logWriter)
+
+	testingLogger := &Logger{
+		consoleLevel: zap.NewAtomicLevelAt(getZapLevel("debug")),
+		fileLevel:    zap.NewAtomicLevelAt(getZapLevel("info")),
+	}
+
+	logWriterCore := zapcore.NewCore(makeEncoder(true), logWriterSync, testingLogger.consoleLevel)
+
+	testingLogger.zap = zap.New(logWriterCore,
+		zap.AddCallerSkip(1),
+		zap.AddCaller(),
+	)
+	return testingLogger
+}