[MM-28423] Implement ImportDelete job (#16588)

* Implement ImportDelete job

* Add missing translation

* Improve logging

* Avoid deleting the file in case of errors

app/import.go

@@ -277,7 +277,7 @@ func (a *App) ListImports() ([]string, *model.AppError) {
 	results := make([]string, 0, len(imports))
 	for i := 0; i < len(imports); i++ {
 		filename := filepath.Base(imports[i])
-		if !strings.HasSuffix(filename, incompleteUploadSuffix) {
+		if !strings.HasSuffix(filename, IncompleteUploadSuffix) {
 			results = append(results, filename)
 		}
 	}