refactored `check_missing_formats_when_decompressing` to be aware of
missing extensions and unsupported extensions in order to give a more
detailed error message
Ouch check for file signatures to be sure that the file indeed has the
correct format as inferred by extension, when that fails, we output a
message explaining that Ouch wasn't able to confirm the format, however,
previous message was confusing with the other extension detection ones
