Changes to filename_template checks

[abishekg7]

Previously, if two active, output stream definitions in the streams. file specified the same string as the filename_template attribute, the corresponding MPAS CORE would crash with an error message. This was also the case for when one of the streams, sharing the filename_template, included an inactive package, hence effectively making it inactive. The existing logic to perform stream uniqueness checks in src/framework/xml_stream_parser.c did not have the information about which packages associated with a stream were active, and hence did not account for inactive packages.

This PR introduces a new subroutine MPAS_stream_mgr_check_filename_template in src/framework/mpas_stream_manager.F to check for unique filename_templates only for streams that are both active, output streams and are not associated with packages that are currently inactive. This subroutine is called from within MPAS_stream_mgr_validate_streams.

The previous logic to check for unique filename_template attributes in src/framework/xml_stream_parser.c has been removed, while retaining the checks for unique stream names

[mgduda]

I've run a few quick tests, and it looks like the core logic is now functioning as expected. I had just a couple of ideas that might clean up the implementation:

1. The outer loop (with stream1_cursor) could cycle on anything other than an active output stream, and that might obviate the need for checks like (stream1_input .and. stream2_input) in the inner loop.
2. If the inner loop (with stream2_cursor) iterated only over streams that occur in the stream list after stream1_cursor, that would eliminate duplicate error messages (e.g., "Found identical values ... for ... foobar_1 and foobar_2" and later "Found identical values ... for ... foobar_2 and foobar_1").