... by employing fuzz, or "lowering the similarity factor". The
replacements (if found) are saved among the artifacts, and serves as
potential drop-in-replacements for outdated images). The main use case
for this is when the font configuration in Tails changes, which
normally invalidates a large part of our images given that our default
high similarity factor.

We also add the `--fuzzy-image-matching` where the replacements are
used in case of FindFailed, so the tests can proceed beyond the first
FindFailed. The idea is that a full test suite run will produce
replacements for potentially *all* outdated images.