[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

app/command_groupmsg_test.go

@@ -42,7 +42,7 @@ func TestGroupMsgUsernames(t *testing.T) {
 }
 
 func TestGroupMsgProvider(t *testing.T) {
-	th := Setup().InitBasic()
+	th := Setup(t).InitBasic()
 	defer th.TearDown()
 
 	user3 := th.CreateUser()