MB-9484: Move most of Producer logic into TapProducer

A lot of the logic in the Producer class will not be used
by the UprProducer. This change moves that logic back into
the TapProducer class.

Change-Id: If04715468340e848d857e8641407eaa75e6035aa
Reviewed-on: http://review.couchbase.org/30847
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>