Selectively demote long-int 1.4-1.8, remove ambiguous constructors

https://github.com/linkedin/avro-util/pull/590 and https://github.com/linkedin/avro-util/pull/591 to add demotion support long to int in avro 1.4-avro 1.8

https://github.com/linkedin/avro-util/pull/592 reverts additional duplicate setters for long/int types.