save several GB of memory on just load

[vtjnash]

This fixes all of Sparse, IO, Array, and Misc to save about 2 GB for a 1000x improvement on those

julia> varinfo(BaseBenchmarks, all=true, sortby=:size)
  name                           size summary                                               
  ––––––––––––––––––––––– ––––––––––– ––––––––––––––––––––––––––––––––––––––––––––––––––––––
  BaseBenchmarks          272.275 MiB Module                                                
  SUITE                   265.295 MiB 23-element BenchmarkGroup([])                         
  LinAlgBenchmarks        216.710 MiB Module                                                
  BroadcastBenchmarks      30.804 MiB Module                                                
  UnionBenchmarks           8.505 MiB Module                                                
  SIMDBenchmarks            5.948 MiB Module                                                
  CollectionBenchmarks      4.351 MiB Module                                                
  ProblemBenchmarks         2.576 MiB Module                                                
  InferenceBenchmarks       2.078 MiB Module                                                
  ArrayBenchmarks           1.464 MiB Module                                                
  MiscellaneousBenchmarks 987.657 KiB Module                                                
  ShootoutBenchmarks      971.345 KiB Module                                                
  TupleBenchmarks         913.608 KiB Module                                                
  RandomBenchmarks        640.623 KiB Module                                                
  AllocBenchmarks         610.874 KiB Module                                                
  ScalarBenchmarks        537.010 KiB Module                                                
  SparseBenchmarks        416.740 KiB Module                                                
  StringBenchmarks        333.805 KiB Module                                                
  SortBenchmarks          150.063 KiB Module                                                
  FindBenchmarks          124.890 KiB Module                                                
  DatesBenchmarks         118.167 KiB Module                                                
  IOBenchmarks             71.189 KiB Module                                                
  MicroBenchmarks          52.814 KiB Module                                                
  ParallelBenchmarks        7.098 KiB Module                                                
  FrontendBenchmarks        5.248 KiB Module