fix: fix generated `getindex` and `length` for `MTKParameters`#3997

AayushSabharwal merged 2 commits intoSciML:masterSciML/ModelingToolkit.jl:masterfrom

AayushSabharwal:as/fix-subset-tunables-adAayushSabharwal/ModelingToolkit.jl:as/fix-subset-tunables-adCopy head branch name to clipboard