MM-16524 Migrate "LinkMetadata.Get" to Sync by default (#11376)

* Update LinkMetadata.Get store and interface

* Update mocks with make store-mocks

* Update tests and implementation

* Avoid casting LinkMetadata.Data

* Fix indent

* Make error more explicit

* Fix indent (was containing spaces)

* Test value returned by LinkMetadata().Get()

store/storetest/mocks/LinkMetadataStore.go

@@ -14,19 +14,28 @@ type LinkMetadataStore struct {
 }
 
 // Get provides a mock function with given fields: url, timestamp
-func (_m *LinkMetadataStore) Get(url string, timestamp int64) store.StoreChannel {
+func (_m *LinkMetadataStore) Get(url string, timestamp int64) (*model.LinkMetadata, *model.AppError) {
 	ret := _m.Called(url, timestamp)
 
-	var r0 store.StoreChannel
-	if rf, ok := ret.Get(0).(func(string, int64) store.StoreChannel); ok {
+	var r0 *model.LinkMetadata
+	if rf, ok := ret.Get(0).(func(string, int64) *model.LinkMetadata); ok {
 		r0 = rf(url, timestamp)
 	} else {
 		if ret.Get(0) != nil {
-			r0 = ret.Get(0).(store.StoreChannel)
+			r0 = ret.Get(0).(*model.LinkMetadata)
 		}
 	}
 
-	return r0
+	var r1 *model.AppError
+	if rf, ok := ret.Get(1).(func(string, int64) *model.AppError); ok {
+		r1 = rf(url, timestamp)
+	} else {
+		if ret.Get(1) != nil {
+			r1 = ret.Get(1).(*model.AppError)
+		}
+	}
+
+	return r0, r1
 }
 
 // Save provides a mock function with given fields: linkMetadata