Make router take up less space for verbs

As is, the router designates routes for every possible boost verb, of
which there are 31.  In bmcweb, we only make use of 6 of those verbs, so
that ends up being quite a bit of wasted space and cache non-locality.

This commit invents a new enum class for declaring a subset of boost
verbs that we support, and a mapping between bmcweb verbs and boost
verbs.

Then it walks through and updates the router to support converting one
to another.

Tested:
Unit Tested
Redfish Service Validator performed on future commit

Signed-off-by: Ed Tanous <edtanous@google.com>
Signed-off-by: Edward Lee <edwarddl@google.com>
Change-Id: I3c89e896c632a5d4134dbd08a30b313c12a60de6