Create `JsonWriteFeature` to move JSON-specific `JsonGenerator.Feature`s to

[cowtowncoder]

(note: similar to #467)

As with JsonParser.Feature, more than half of entries are JSON-specific and not general-purpose; so for 2.10 (and esp. 3.0) let's cleave those out to new JsonWriteFeature.
And once that is done, consider adding something like StreamWriteFeature for format-agnostic general settings.