ISO19110 / ISO19115-3.2008 / Fix indexing of multiple feature type aliases

[josegar74]

Test case:

1. Create an ISO19110 metadata and assign 2 FeatureType aliases.

2. Without the fix the following indexing error occurs:

Error on line 104 of index.xsl:
  XPTY0004: A sequence of more than one item is not allowed as the first argument of
  util:escapeForJson() ("Variable Name", "Variable Info") 

---

The UI is updated to concatenate the values, requiring to reindex the ISO19110 to process the aliases as an array.

Checklist

• I have read the contribution guidelines
• Pull request provided for main branch, backports managed with label
• Good housekeeping of code, cleaning up comments, tests, and documentation
• Clean commit history broken into understandable chucks, avoiding big commits with hundreds of files, cautious of reformatting and whitespace changes
• Clean commit messages, longer verbose messages are encouraged
• API Changes are identified in commit messages
• Testing provided for features or enhancements using automatic tests
• User documentation provided for new features or enhancements in manual
• Build documentation provided for development instructions in README.md files
• Library management using pom.xml dependency management. Update build documentation with intended library use and library tutorials or documentation

[fxprunayre]

LGTM and you can also apply it to https://github.com/geonetwork/core-geonetwork/blob/main/schemas/iso19115-3.2018/src/main/plugin/iso19115-3.2018/index-fields/index.xsl#L1070

[josegar74]

@fxprunayre thanks for checking it, the pull request is updated.