Use ncml in datasetscan

[tdrwenski]

Description of Changes

This fixes https://github.com/Unidata/tds/issues/403 (TDS tests in https://github.com/Unidata/tds/pull/404).

NetCDF datasetScan datasets opened through cdmremote, wms or opendap use this mergeNcml function to add ncml to the dataset. This does not apply enhancements even if the ncml has enhance="all". This PR would parse and use enhancements set in ncml.

PR Checklist

• [ ] Link to any issues that the PR addresses
• [ ] Add labels
• [ ] Open as a draft PR until ready for review
• [ ] Make sure GitHub tests pass
• [ ] Mark PR as "Ready for Review"