Add default visibility implementations

It would reduce boilerplate if JSON-B implementations were required to ship with some often-needed visibility strategies, such as (up for discussion):
- `PropertyNamingStrategy.PUBLIC_PROPERTY`: Use public getters / setters, or public fields (if no corresponding getter / setter) for (de-)serialization. Default behavior.
- `PropertyNamingStrategy.PUBLIC_GETTER_SETTER`: Use public getters / setters for (de-)serialization.
- `PropertyNamingStrategy.PUBLIC_FIELDS`: Use public fields for (de-)serialization. Corresponding getters / setters that exist for the fields must be used.
- `PropertyNamingStrategy.FIELDS`: Use fields (of any visibility) for (de-)serialization. Corresponding getters / setters that exist for the fields must be used.

Maybe add others as well.

For convenience, these constants should be added to the `PropertyNamingStrategy` interface.

Start by reviewing the PropertyNamingStrategy interface and the five existing comments to determine which visibility strategies and semantics are agreed. The issue is complete when the accepted constants and their behavior are defined and added to the interface, with verification covering the resulting visibility rules.

Written by the indexing model from the issue text.