fcl-db: dataset: after rev.26661 some tests are broken. They use locate in form: Locate('ID', VarArrayOf([1])); So one field with one element array.
This patch takes into account:
- most common situation is, when we assign simple variant (not array) to one field, so optimise code to it
- when assign array to one field, do not restrict array dimensions on "dataset level" , but postpone it to "field level" and let field raise SFieldValueError if it cannot handle supplied variant value.

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@26746 3ad0048d-3df7-0310-abae-a5850022a9f2