#1233 CifToBddExprOnlySupportedExprsCheck: more caching for algebraic variable references being checked

• End-user visible changes:
  • CIF data-based synthesis and the CIF controller properties checker (for BDD-based checks) now have additional caching, to prevent duplicate work, and in certain situations even prevent exponential blow-ups. This concerns: the result of the pre-condition check for supported expression forms. It was already cached for references to algebraic variables being checked in predicates, but not yet in other expressions.

Closes #1233 (closed)