subjects: improve search with CompositeSuggestQueryParser

[ptamarit]

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Description

• Fixes Improve MeSH search results #447 (see details in linked issue)
• The feature allowing to search by prefix (e.g. EuroSciVoc:dementia) used to have a corresponding UI automatically adding the prefixed filter.
  Now that this is not in the UI anymore, since this search behavior is not documented, and since the search results of FilteredSuggestQueryParser are not good, we are proposing to:
  • Deprecate FilteredSuggestQueryParser
  • Use the recently introduced CompositeSuggestQueryParser, which narrows down results as more search terms are added

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