Don't check units during initialization

[ctessum]

...because initialization problems don't correctly handle units and units have already been checked during system initialization.

Checklist

• [X] Appropriate tests were added
• [X] Any code changes were done in a way that does not break public API
• [X] All documentation related to code changes were updated
• [X] The new code follows the contributor guidelines, in particular the SciML Style Guide and COLPRAC.
• [X] Any new documentation only uses public API

Additional context

Fixes #3086

[ChrisRackauckas]

@AayushSabharwal can you incorporate this post your PR?

[ChrisRackauckas]

@AayushSabharwal can you rebase this onto your larger change?

[AayushSabharwal]

Sure, sorry for missing this earlier.

[AayushSabharwal]

I have the format commit ready. Once tests pass, I'll push it and merge so we don't rerun CI unnecessarily.

[AayushSabharwal]

All tests pass, barring the homotopy continuation ones fixed in #3158