Allow combination of `@JsonValue`, `@JsonRawValue` somehow

[cowtowncoder]

(for background see FasterXML/jackson-databind#1938)

Although naming of @JsonRawValue might indicate combination of @JsonValue and "do not encode", it actually works as refinement for regular properties, that is, combination of @JsonProperty and "do not encode".

But in some cases it would be beneficial to allow former interpretation.

One possibility would be to add a new property in @JsonValue -- this seem more natural than doing the reverse (adding something in @JsonRawValue to indicate "this is the sole output like @JsonValue, not property).