[[issue31392] add convenience functions for constructing container coders from other AvroCoders rather than from AvroEncoder, AvroDecoder plus add some comments
[no issue] InsecureContext should default to false
[issue31392, issue31391] add doc comments for more Avro coders, plus move generic collection utilities up to base from avro
[issue31391] close action of sequenceResultBindings in a block to prevent weird ambiguous ASTs (when prettyprinted) from being created
[issue31393, issue31392, issue31391] fix constructAndAssign for singleton types (that is, objects) so that new <object> doesn't get generated by macros
[issue31393] working JSON (Jackson) format for interchange gen 2