supported non-deterministic functions are evaluated prior to push-down

Defect Tracker #24735: We currently will not actually push down non-deterministic functions even if they are supported, since the evaluateexpressionvisitor will replace them with constant values. For example rand will be pre-evaluated before being sent to sqlserver (however sqlserver does not correctly support non-deterministic functions anyway). We may need to actually not support non-deterministic functions in sqlserver or other sources that do not handle them properly.