Support Const Propagation for Variables

[tustvold]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

Currently the SimplifyRule creates its own ExecutionProps from the OptimizerConfig, rather than this being propogated through correctly. The resulting ExecutionProps therefore lacks any VarProvider and so const propagation is not possible for variables.

Describe the solution you'd like

These variables should be available at optimization time, much like query_execution_start_time, to allow for const propagation to work correctly.

Describe alternatives you've considered

Additional context

#4629 tracks making ExecutionProps a trait
#2666 moved OptimizerRule away from using ExecutionProps in favor of a OptimizerConfig