Remove hidden files from indexer results (#4325)

* Added functionality to not display hidden files

* Added interfaces for seperating db layer

* Updated variable naming and refactored Database connection class

* Added tests for WindowsSearchAPI class

* Fixed nit with braces

* Added function to test that all connections from database are closed

src/modules/launcher/Plugins/Microsoft.Plugin.Indexer/Main.cs

@@ -30,7 +30,7 @@ namespace Microsoft.Plugin.Indexer
         private PluginJsonStorage<Settings> _storage;
 
         // To access Windows Search functionalities
-        private readonly WindowsSearchAPI _api = new WindowsSearchAPI();
+        private readonly WindowsSearchAPI _api = new WindowsSearchAPI(new OleDBSearch());
 
         // Reserved keywords in oleDB
         private string ReservedStringPattern = @"^[\/\\\$\%]+$";