after reviewing the patch I have some concerns about CodecProvider. I think its a little bit confusing how the CodecProvider/CoreCodecProvider hierarchy works today, and a bit dangerous how we delegate over this class.
For example, if we add a new method to CodecProvider, we need to be sure we add the 'delegation' here every time or stuff will start acting strange.
For this reason, I wonder if CodecProvider should be an interface: the simple implementation we have in lucene is a hashmap, but Solr uses fieldType lookup. This would parallel how SimilarityProvider works.
If we want to do this, I think we should open a separate issue... in fact I'm not even sure it should block this issue since in my opinion its a shame you cannot manipulate codecs in Solr right now... but I just wanted to bring it up here.