Factor out commonalities in xlated_*_prefix() methods.
Factor out commonalities in xlated_*_prefix() methods.

Use in _xlated_prefixes().

_xlated_prefixes() evaluated everything to a list. The point of making
_xlated_binary_prefix() to evaluate to a lazy comprehension was to delay
evaluation, but _xlated_prefixes() evaluated everything, so there was little
point. Now evaluation is actually delayed until needed.

Signed-off-by: mulhern <7b51bcf507bcd7afb72bf8663752c0ddbeb517f6@redhat.com>

rvykydal/blivet,rhinstaller/blivet,dwlehman/blivet,vpodzime/blivet,vojtechtrefny/blivet,vpodzime/blivet,jkonecny12/blivet,AdamWill/blivet,dwlehman/blivet,rvykydal/blivet,jkonecny12/blivet,rhinstaller/blivet,AdamWill/blivet,vojtechtrefny/blivet