Eliminate surprises from ansys.fluent.core.services.field_data.FieldData

[seanpearsonuk]

Problem is that get_fields etc is in the same interface as all this query builder stuff. This doesn't sit together properly and is baffling on first view. Queries could be separate objects returned by FieldData. The programmer would build the query and use it directly via its own interface only.

• rm get_fields etc from FieldData
• rm add_get_etc methods from FieldData
• create new query class
• make query objects createable via FieldData public interface
• add interface to query objects so that query can be built and executed
• add simple "single shot" interface to FieldData