Combine Compositions and Composition type

In pkg/discovery/types.go,
There are two similar types that need to be refactored/combined together.
Composition ("Used for final output")
and
Compositions ("Used for api functionality")

Start in pkg/discovery/types.go by reading the Composition and Compositions definitions and checking their usages. Trace how each supports final output and API functionality, then determine the combined type's required behavior and update the affected references. Done means the duplicate types are combined without breaking those two uses.

Written by the indexing model from the issue text.