Níma: shortcut methods for media support(s)

[Tomas-Kraus]

Issue #6278 follow up.

In reactive, we can configure media support directly on web server builder. This would require a new interface (e.g. MediaSupport) to be created by the provider.
So users can register JsonSupport.create() instead of creating a new instance of a service loader provider implementation

[tomas-langer]

The new approach should support:

• customization of underlying features (custom ObjectMapper for Jackson, JSON-B and JSON-P as well)
• using config to set up the underlying features
• customizing supported media types

The config based approach would ideally work for the service providers as well, if feasible (e.g. if I construct my MediaContext from Config)