Package load time regressions in 1.12

[KristofferC]

I think this deserves a separate issue to track this.

❯ julia +nightly --project=@MTK_1.13 -e '@time using ModelingToolkit'
  3.292820 seconds (8.19 M allocations: 478.546 MiB, 7.74% gc time, 4.13% compilation time: 36% of which was recompilation)

  ❯ julia +1.11 --project=@MTK_1.11 -e '@time using ModelingToolkit'
  2.454841 seconds (5.07 M allocations: 346.203 MiB, 7.39% gc time, 3.76% compilation time: 31% of which was recompilation)

  ❯ julia +1.10 --project=@MTK_1.10 -e '@time using ModelingToolkit'
  2.507505 seconds (4.80 M allocations: 359.739 MiB, 10.68% gc time, 2.24% compilation time: 34% of which was recompilation)

Nightly has a big bump in load time.