GEOPY-2337: Parallelize dpred for EM simulations

[domfournier]

GEOPY-2337 - Parallelize dpred for EM simulations

Summary

PR Checklist

• If this is a work in progress PR, set as a Draft PR
• Linted my code according to the style guides.
• Added tests to verify changes to the code.
• Added necessary documentation to any new functions/classes following the
  expect style.
• Marked as ready for review (if this is was a draft PR), and converted
  to a Pull Request
• Tagged @simpeg/simpeg-developers when ready for review.

Reference issue

What does this implement/fix?

Additional information