Group sending of datapoints

[rafaeling]

This PR implements the group sending of datapoints by a newly defined json file.

• Databroker-perf creates two gRPC channels (one for the provider and one for the subscriber) shared among groups.

• Each provider will update its group signal values to the Databroker at the cycle time specified (in milliseconds) in the JSON configuration file provided.

• config_group.json file:

{
  "groups": [
    {
      "group_name": "Frame 1",
      "cycle_time_ms": 10,
      "signals": [
        {
          "path": "Vehicle.Speed"
        }
      ]
    },
    {
      "group_name": "Frame 2",
      "cycle_time_ms": 20,
      "signals": [
        {
          "path": "Vehicle.IsBrokenDown"
        },
        {
          "path": "Vehicle.IsMoving"
        },
        {
          "path": "Vehicle.AverageSpeed"
        }
      ]
    }
  ]
}

• Run seconds test parameter implemented instead of iterations parameter since all groups should end at the same exact time.

• --detail-output flag added to extend the test result view.

• Max number of groups defined to 10.

• Check docu for more info: https://github.com/eclipse-kuksa/kuksa-perf/blob/b89e1c906d1d879e99d0dd3e01b2a1f07f9d8e97/README.md

• Use first subscribed values to publish correct values and avoid app from blocking

[mikehaller]

LGTM, some minor hints for potential improvement, but nothing critical.

[erikbosch]

Looks ok to me. Did a sanity test and it seemed to work ok

[argerus]

This currently doesn't work with sdv.databroker.v1. I think it has to do with the changes introduced to share a Provider between multiple senders.

My guess is that the issue stems from introducing an Arc<RwLock<<_>> around the provider. I think it would be better to use a clonable Publisher that would wrap the underlying Sender side of the channel that the provider uses to queue up things to publish.

[argerus]

I guess this is good enough now to enable specifying cycle time per signal.. Not really happy with a number of regressions, but lets improve those in follow up PRs