The classifier can load and merge rules from multiple files.
A basic iana enhanced status codes ruleset is provided.
A deployment can define their own to augment that set.
This commit is just the core classifier functionality; it
is not yet connected to kumod.
The classification enum is a bit of an amalgam of categories
defined by other well-known vendors/products and the categories
defined by IANA. Some classifications have no corresponding
rules at the current time.