This PR rehauls /collections/{}/optimizations endpoint.

• Now this endpoint contains the following fields:
  • summary (replaces old summary in pending)
  • running (was ongoing) - list
  • queued (new) - list, predicted by OptimizerPlanner
  • completed - list
  • idle_segments (new) - list of good segments that don't require optimizations
• Previously, running/completed lists were containing naked ProgressTrees.
  • In this PR, they are wrapped with additional meta-information.
  • uuids are included to let the UI refresh currently selected progress tree.
  • The difference, illustrated:

     "running": [
    +  {
    +    "uuid": "b17f761d-be66-4cab-b931-3f631c746066",
    +    "segments": [
    +      {"uuid": "ea103d7a-f379-4b37-814c-9f8b6400c321", "points_count": 12345}
    +    ],
    +    "optimizer": "indexing",
    +    "status": "optimizing",
    +    "progress":
           { /* progress tree */ },
    +  }
     ]

• New query parameter ?with to control whether to include new optional fields.
  • To include all fields, use ?with=queued,completed,idlle_segments.
  • Why: these lists might be very chunky.
  • Why running is not optional: if we need just a single number of current optimizations, then we can add this number it to GET /collections/{} endpoint.
  • The old parameter ?completed=true is replaced with ?with=completed.
• Use-case for OptimizationSegmentInfo (idle_segments[], queued[].segments[], running[].segments[]):
  The UI might visualize the collection as a bunch of rectangles; with color/size based on the status/points count. (perhaps it might look like the old defrag) UUIDs can help keep ordering/transitions.

Example output:

{
  "summary": {
    "queued_optimizations": 8,
    "queued_segments": 8,
    "queued_points": 50400,
    "idle_segments": 8
  },

  "running": [
    {
      "uuid": "9254c533-f78e-4b14-9935-593ef2bc8519",
      "optimizer": "indexing",
      "status": "optimizing",
      "segments": [
        {"uuid": "bfcd34c7-eebd-47b1-a30e-781ac2a28dc7", "points_count": 6300}
      ],
      "progress": { /* progress */ }
    },
    /* … */
  ],

  "queued": [
    {
      "optimizer": "indexing",
      "segments": [
        {"uuid": "95da2479-48d5-48a3-bfb9-a89f2a9a1c7f", "points_count": 6300}
      ]
    },
    /* … */
  ],

  "completed": [
    {
      "uuid": "8f7a3e39-e96f-4e8d-aad5-3d04eddd08f0",
      "optimizer": "indexing",
      "status": "done",
      "segments": [
        {"uuid": "67a1160a-fdf0-4765-8f77-d941dddb218b", "points_count": 6332}
      ],
    },
    /* … */
  ],

  "idle_segments": [
    {"uuid": "fbc4e2f0-763c-4a07-9763-74b91bf06419", "points_count": 5060},
    {"uuid": "852914c0-3267-4eba-b4f0-41a0b97fab04", "points_count": 7260},
    {"uuid": "01573268-2b43-4959-98be-faeca6c39582", "points_count": 7024},
    /* … */
  ]
}