fix: fix `fast_substitute` folding array of symbolics#1398

ChrisRackauckas merged 5 commits intoJuliaSymbolics:masterJuliaSymbolics/Symbolics.jl:masterfrom

AayushSabharwal:as/fast-substitute-arrayAayushSabharwal/Symbolics.jl:as/fast-substitute-arrayCopy head branch name to clipboard