Migrate metrics from OpenCensus to OpenTelemetry

[infernus01]

Changes

Migrates Operator metrics from the deprecated OpenCensus library to OpenTelemetry.

• Replace OpenCensus imports (go.opencensus.io/stats, stats/view, tag) with OpenTelemetry (go.opentelemetry.io/otel, otel/attribute, otel/metric) in tektonpipeline/metrics.go, tektontrigger/metrics.go, tektonchain/metrics.go, and tektonresult/metrics.go
• Convert counter metrics to metric.Int64Counter and gauge metric to metric.Float64Gauge
• Rewrite tektonresult/metrics_test.go to use sdkmetric.ManualReader for asserting actual collected metric values
• Update config-observability.yaml to use OTel configuration keys (metrics-protocol, tracing-protocol) and remove legacy OpenCensus keys
• Bump knative.dev/pkg to v0.0.0-20260318013857-98d5a706d4fd (OTel observability stack)
• Regenerate client code via ./hack/update-codegen.sh
  /kind feature

closes : #3307
fixes : #3331

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Release Notes

Migrated operator metrics from OpenCensus to OpenTelemetry.

ACTION REQUIRED:

1. Configuration key change
   Replace metrics.backend-destination with metrics-protocol in your tekton-config-observability ConfigMap.

2. Custom metric name changes

   ┌──────────────────────────────────────────────────────────────┬──────────────────────────────────────────────────────────────┐
   │ Old Metric Name (OpenCensus)                                 │ New Metric Name (OpenTelemetry)                              │
   ├──────────────────────────────────────────────────────────────┼──────────────────────────────────────────────────────────────┤
   │ tekton_operator_lifecycle_pipeline_reconcile_count           │ tekton_operator_lifecycle_pipeline_reconcile_total           │
   │ tekton_operator_lifecycle_trigger_reconcile_count            │ tekton_operator_lifecycle_trigger_reconcile_total            │
   │ tekton_operator_lifecycle_chains_reconciled                  │ tekton_operator_lifecycle_chains_reconciled_total            │
   │ tekton_operator_lifecycle_results_reconciled                 │ tekton_operator_lifecycle_results_reconciled (unchanged)     │
   └──────────────────────────────────────────────────────────────┴──────────────────────────────────────────────────────────────┘

3. Infrastructure metric renaming

   ┌──────────────────────────────────────────────────────────────────┬────────────────────────────────────────────────────┐
   │ Old Metric Name (OpenCensus)                                     │ New Metric Name (OpenTelemetry)                    │
   ├──────────────────────────────────────────────────────────────────┼────────────────────────────────────────────────────┤
   │ tekton_operator_lifecycle_workqueue_adds_total                   │ kn_workqueue_adds_total                            │
   │ tekton_operator_lifecycle_workqueue_depth                        │ kn_workqueue_depth                                 │
   │ tekton_operator_lifecycle_workqueue_queue_latency_seconds        │ kn_workqueue_queue_duration_seconds                │
   │ tekton_operator_lifecycle_workqueue_work_duration_seconds        │ kn_workqueue_process_duration_seconds              │
   │ tekton_operator_lifecycle_workqueue_unfinished_work_seconds      │ kn_workqueue_unfinished_work_seconds               │
   │ tekton_operator_lifecycle_client_latency                         │ http_client_request_duration_seconds               │
   │ tekton_operator_lifecycle_client_results                         │ kn_k8s_client_http_response_status_code_total      │
   │ tekton_operator_lifecycle_go_*                                   │ go_*                                               │
   │ tekton_operator_lifecycle_reconcile_count                        │ removed (use kn_workqueue_adds_total)              │
   │ tekton_operator_lifecycle_reconcile_latency                      │ removed (use kn_workqueue_process_duration_seconds)│
   └──────────────────────────────────────────────────────────────────┴────────────────────────────────────────────────────┘

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[infernus01]

I don't see we are consuming eventing pkg anywhere in the code.

[khrm]

I think we should remove metrics in the operator. These aren't used by customers or users. It was for some telemetry, but it's not working properly for that also.

If I get time, I would write more on that.

[jkhelil]

I think we should remove metrics in the operator. These aren't used by customers or users. It was for some telemetry, but it's not working properly for that also.

If I get time, I would write more on that.

We have stories to enhance overall metrics on operator, to move to olm level 3 and for 4, i didnt dig into details for these levels, but lets not remove metrics for now, until we tackle properly those stories please

[tekton-robot]

@infernus01: PR needs rebase.

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