Enabled the Natura 2000 download link in Sites Other Resources.
Closes #18633
Changed the Species Legal search to reduce the number of domain objects and unify the search functionality in one object. Removed the other (now unused) domain objects.
The search is now done by the ID_DC field and not by document name and annex number, as some of the documents do not have annex numbers.
The document name dropdown uses the alternative name in DC_INDEX, so it has to be filled.
Closes #20256