Expose NP FieldFormats service to server side

[lizozom]

The fieldFormats service is used on the server side as well.
At the moment, it resides in src/legacy/ui/field_formats/mixin/field_formats_service.ts and only the FE plugin exposes it.

We should expose the field registry from the server side plugin at data.fieldFormats.

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)

[lukeelmers]

Just noting that this is a blocker for reporting migrating to new platform.

cc @tsullivan