Define RAID level for LV and use it to determine required PV space
Define RAID level for LV and use it to determine required PV space

We already support various segment types for LVs to some extent. However, we
need to get a better picture of how much space on such LVs' PVs is required. We
already have a code for that, so let's just use it.

This unfortunately requires the LVPVSpec to have read-write attributes/fields
and thus it cannot be a namedtuple. We should probably come up with some
"read-write namedtuple" thing for cases like this in the future.

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