core.go: Remove legacy methods {Vom,Gob}{En,De}code
core.go: Remove legacy methods {Vom,Gob}{En,De}code

The RoutingID is never actually serialized by vom (or gob), so
these methods are pointless.  In addition the new vom doesn't
actually support Vom{En,De}code.

Change-Id: Ib0df4d52c598374c74faf45d8fe14a7af278e7e1

vanadium/go.v23,vanadium/go.v23,vanadium/go.v23