(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 just realized `resolve_processors` appears to be identical between Linux and OSX (and it should be for all platforms, since it's just a translation from the structured fact to the flat facts), can we move the implementation into the base class?