[Improvement]: Support distinct error in error semtype integration

[lochana-chathura]

Description

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// distinctId must be >= 0
public function errorDistinct(int distinctId) returns SemType {
   BddNode bdd = bddAtom(-distinctId - 1);
   return basicSubtype(BT_ERROR, bdd);
}

• distinct error<R> is equivalent to distinct error & error<R>.

• distinct error<R> semtype can be modeled as Core.intersect(errorDistinct(id), err) where err is the semtype of error<R>.