Add convert-to-nia command-line program

Together with similar programs in other repositories, this helps find
disagreements between Chromium's, Skia's and Wuffs' image decoders.

Change-Id: I9a0d8aabb47b1d5bd29f9139755e76bf56ab4bbe
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/290618
Commit-Queue: Leon Scroggins <scroggo@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
2 files changed