(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.
A stylistic comment: I'd prefer an early return here rather than indenting the reset of the function.  In C++ you should (generally) never fear an early return :)