fix: only evaluate required keys of varmap in `process_SciMLProblem`#3156

ChrisRackauckas merged 3 commits intoSciML:masterSciML/ModelingToolkit.jl:masterfrom

AayushSabharwal:as/varmap-partial-evalAayushSabharwal/ModelingToolkit.jl:as/varmap-partial-evalCopy head branch name to clipboard