Return additional info about Gitaly in internal agent_info and project_info APIs

The internal APIs we are introducing in !33228 (merged) should return more API about Gitaly. An example helper is here https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/api/helpers/internal_helpers.rb#L121.

Let's restructure /agent_info response like so:

{
  "project_id": ...,
  "agent_id": ...,
  "agent_name": ...,
  "gitaly_info": {
    "address": ...,
    "token": ...,
    "features": ...
  },
  "gitaly_repository": {
    "storage_name": ...,
    "relative_path": ...,
    "gl_repository": ...,
    "gl_project_path": ...
  }
}

Let's restructure /project_info response like so:

{
  "project_id": ...,
  "gitaly_info": {
    "address": ...,
    "token": ...,
    "features": ...
  },
  "gitaly_repository": {
    "storage_name": ...,
    "relative_path": ...,
    "gl_repository": ...,
    "gl_project_path": ...
  }
}