Adding changes to separate unit tests and integration tests (#13670)

* Introducing unit (not integration) tests for the app layer

* Initial support for unit tests at the API

* Adding unit tests support to the store layer

* Add unit tests support in commands

* Adding last tests needed for run unit tests properly

* Fixing govet

* Removing some duplication

* Fixing tests

* Fixing tests

* Not compiling test helpers with the main module for api

* Revert "Not compiling test helpers with the main module for api"

This reverts commit 36a199bbe0f7503f665f5d6c7b41c53aabc2e54f.

* Fixing tests

* Fixing unit tests

* More consistency between api4/apiteslib.go and app/helper_test.go

* Renaming things to make more obvious the new Setup functions purpose

* Reverting change in go.sum

* Start with empty mock for app layer

* Start with empty mock for api layer

* Start with empty mock for web layer

* Renaming SetupWithStoreMockConfig to SetupConfigWithStoreMock

* Fixing tests on web package

* Removing unnecesary function

app/export_test.go

@@ -44,7 +44,7 @@ func TestReactionsOfPost(t *testing.T) {
 }
 
 func TestExportUserNotifyProps(t *testing.T) {
-	th := Setup(t)
+	th := SetupWithStoreMock(t)
 	defer th.TearDown()
 
 	userNotifyProps := model.StringMap{
@@ -112,7 +112,7 @@ func TestExportUserChannels(t *testing.T) {
 }
 
 func TestDirCreationForEmoji(t *testing.T) {
-	th := Setup(t)
+	th := SetupWithStoreMock(t)
 	defer th.TearDown()
 
 	pathToDir := th.App.createDirForEmoji("test.json", "exported_emoji_test")
@@ -122,7 +122,7 @@ func TestDirCreationForEmoji(t *testing.T) {
 }
 
 func TestCopyEmojiImages(t *testing.T) {
-	th := Setup(t)
+	th := SetupWithStoreMock(t)
 	defer th.TearDown()
 
 	emoji := &model.Emoji{