Fix Prometheus job execution counters by removing duplicate metric-family emission

[Copilot]

Proposed changes

PR #1885 attempted to expose job execution success/failure counters in /metrics, but the counters were still unreliable due to duplicate emission through two metric systems under the same metric names.
This update makes Prometheus export deterministic by emitting these counters through a single collector path.

• Metric registration

  • Added native Prometheus counters in dkron/job_metrics.go:
    • dkron_job_executions_succeeded_total{job_name=...}
    • dkron_job_executions_failed_total{job_name=...}

• Execution-path wiring

  • Updated Store.SetExecutionDone to increment the native Prometheus counters for success/failure outcomes.
  • Removed go-metrics emission for these two metric names to prevent duplicate metric-family conflicts during gather/scrape.

• Focused regression coverage

  • Added TestSetExecutionDonePrometheusMetrics in dkron/store_test.go to assert both counters increment correctly per job_name label.

if pbe.Success {
    JobExecutionsSucceededTotal.WithLabelValues(execution.JobName).Inc()
} else {
    JobExecutionsFailedTotal.WithLabelValues(execution.JobName).Inc()
}

Types of changes

What types of changes does your code introduce?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• 127.0.0.10
  • Triggering command: /tmp/go-build1174015694/b1335/dkron.test /tmp/go-build1174015694/b1335/dkron.test -test.testlogfile=/tmp/go-build1174015694/b1335/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true ternal/protocompile/internal/cases/cases.go ternal/protocompile/internal/cases/words.go (packet block)
• 127.0.0.11
  • Triggering command: /tmp/go-build1174015694/b1335/dkron.test /tmp/go-build1174015694/b1335/dkron.test -test.testlogfile=/tmp/go-build1174015694/b1335/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true ternal/protocompile/internal/cases/cases.go ternal/protocompile/internal/cases/words.go (packet block)
• 127.0.0.13
  • Triggering command: /tmp/go-build1174015694/b1335/dkron.test /tmp/go-build1174015694/b1335/dkron.test -test.testlogfile=/tmp/go-build1174015694/b1335/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true ternal/protocompile/internal/cases/cases.go ternal/protocompile/internal/cases/words.go (packet block)
• 127.0.0.14
  • Triggering command: /tmp/go-build1174015694/b1335/dkron.test /tmp/go-build1174015694/b1335/dkron.test -test.testlogfile=/tmp/go-build1174015694/b1335/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true ternal/protocompile/internal/cases/cases.go ternal/protocompile/internal/cases/words.go (packet block)
• client.badssl.com
  • Triggering command: /tmp/go-build1174015694/b1349/http.test /tmp/go-build1174015694/b1349/http.test -test.testlogfile=/tmp/go-build1174015694/b1349/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true 4015694/b1025/_p-errorsas pkg/mod/k8s.io/a-ifaceassert ux_amd64/vet -p .io/otel/exporte-atomic -lang=go1.23 ux_amd64/vet (dns block)
• self-signed.badssl.com
  • Triggering command: /tmp/go-build1174015694/b1349/http.test /tmp/go-build1174015694/b1349/http.test -test.testlogfile=/tmp/go-build1174015694/b1349/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true 4015694/b1025/_p-errorsas pkg/mod/k8s.io/a-ifaceassert ux_amd64/vet -p .io/otel/exporte-atomic -lang=go1.23 ux_amd64/vet (dns block)
• untrusted-root.badssl.com
  • Triggering command: /tmp/go-build1174015694/b1349/http.test /tmp/go-build1174015694/b1349/http.test -test.testlogfile=/tmp/go-build1174015694/b1349/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true 4015694/b1025/_p-errorsas pkg/mod/k8s.io/a-ifaceassert ux_amd64/vet -p .io/otel/exporte-atomic -lang=go1.23 ux_amd64/vet (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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