[terafoundation] Prom metrics exporter doesn't reset metrics between updates

[busma13]

This PR makes the following changes:

• The PromMetrics class needs to reset it's list of metrics on each scrape. If it doesn't do this, then all the executions are listed, not just the active ones. resetMetrics() functions were added to PromMetrics and Exporter to reset the prom-client register.
• Add prom_metrics_display_url field to terafoundation. This value will be used as the url default label added to all prom metrics. Defaults to an empty string, making it more obvious that this field is missing from the config.
• Include cluster analytics metrics (GET '/cluster/stats' endpoint results) in the cluster master

ref: #3743

[godber]

Uh, I completely forgot about this ...

https://github.com/terascope/teraslice/commit/49d356cf7dc6583c518f98a4500355c53e173e9f

curl -H "Accept: application/openmetrics-text;" -sS http://localhost:5678/cluster/stats
# TYPE teraslice_slices_processed counter
teraslice_slices_processed{cluster="teraslice-dev1"} 2
# TYPE teraslice_slices_failed counter
teraslice_slices_failed{cluster="teraslice-dev1"} 0
# TYPE teraslice_slices_queued counter
teraslice_slices_queued{cluster="teraslice-dev1"} 0
# TYPE teraslice_workers_joined counter
teraslice_workers_joined{cluster="teraslice-dev1"} 1
# TYPE teraslice_workers_disconnected counter
teraslice_workers_disconnected{cluster="teraslice-dev1"} 0
# TYPE teraslice_workers_reconnected counter
teraslice_workers_reconnected{cluster="teraslice-dev1"} 0

compared to:

curl -sS http://localhost:5678/cluster/stats
{
    "controllers": {
        "processed": 2,
        "failed": 0,
        "queued": 0,
        "job_duration": 3,
        "workers_joined": 1,
        "workers_disconnected": 0,
        "workers_reconnected": 0
    },
    "slicer": {
        "processed": 2,
        "failed": 0,
        "queued": 0,
        "job_duration": 3,
        "workers_joined": 1,
        "workers_disconnected": 0,
        "workers_reconnected": 0
    }
}

We should document the existence of this capability and we should really consider expanding the labels coming out of it or consolidating these metrics in with the new main built in exporter.

[busma13]

teraslice_slices_processed{cluster="teraslice-dev1"} 2

curl localhost:5678
{
    "arch": "arm64",
    "clustering_type": "kubernetes",
    "name": "ts-dev1",
    "node_version": "v18.20.4",
    "platform": "linux",
    "teraslice_version": "v2.3.0"
}

cluster === teraslice.name from the terafoundation, correct? Which is what is returned in the request above.

[godber]

cluster === teraslice.name from the terafoundation, correct? Which is what is returned in the request above.

Correct

[busma13]

We should document the existence of this capability

I added an example in the endpoints-json.md file