glocalvfs: Remove unnecessary and buggy code

The code for stripping the query and fragment from file:// URIs was wrong, as it would not properly strip a query if there was a fragment.

Fortunately, that code was actually useless, as the "stripped URI" was passed to g_filename_from_uri() that does proper stripping itself.

So simply drop this extra unnecessary stripping logic from GLocalVFS's get_file_for_uri() and let g_filename_from_uri() do all the work.

Also add some tests for combined query and fragment, including a fragment with a query marker in it just to be sure it's actually properly handled.