Refactor org.opendaylight.openflowjava.nx.codec.match.AbstractMatchCodec

Layout of AbstractMatchCodec leads to similar problems as addressed in OPNFLWPLUG-1068. Most notably we are forcing the fast path to be megamorphic due to getNxmFieldCode()/getOxmClassCode()/getValueLength() – which can easily be made monomorphic by making them refer to normal fields – but other things done for MatchEntrySerializer apply heree as well.