Common Yaml writer for TEXT and YAML wires.

[alamar]

Right now there's two parsers and each of those has a writer. They end up producing incorrect YAML in some cases, such as putting extra commas in key: value blocks.

There's a reason why there should be two parsers for now, but there's no reason to have more than one writer, which should be conservative in what it emits. In 2.24 one of writers may be removed.