Manifest generation should show full service configuration information

Issue

Currently, if a service for an app was configured with parameters other than name (e.g. the parameters or binding_name field), they will not be shown when generating a manifest.

Context

Let's say we push an app with a manifest like so:

---                                                                                                                                                                                                              
applications:
- name: dora
  services:
  - name: my-service
    binding_name: my-binding
    parameters:
      foo: bar    

When we curl /v3/apps/:guid/manifest, this is what we receive:

---                                                                                                                                                                                                              
applications:
- name: dora
  services:
  - my-service

This could be an issue if one were to try applying a manifest to a different space or org to duplicate an app. It also causes or exacerbates issues with manifest diffs, such as https://github.com/cloudfoundry/cloud_controller_ng/issues/2201, where we cannot generate a proper diff because the logic between that endpoint and the manifest diff generation are shared.

Possible Fix

Always render services in their full configuration, instead of always rendering just their name.

Start by tracing manifest generation for GET /v3/apps/:guid/manifest and inspect the shared logic used by manifest diff generation. Compare the current service rendering with the supplied manifest example; done means generated manifests preserve service fields such as binding_name and parameters rather than only the service name.