(CFACT-63) Add structured processors fact

This commit adds a new 'processors' structured fact, which returns a map
including keys for processor count, physical processor count, and
processor models.

Also, the existing processor facts were updated to take their values from
this new structured fact, rather than resolving them individually.
I'm on board with how you implemented it in Facter: it should be integer in the structured fact, string in the legacy fact.