fix(OTEL): reduce high cardinality in traces and metrics (#9286)

# Which Problems Are Solved

There were multiple issues in the OpenTelemetry (OTEL) implementation
and usage for tracing and metrics, which lead to high cardinality and
potential memory leaks:
- wrongly initiated tracing interceptors
- high cardinality in traces:
  - HTTP/1.1 endpoints containing host names
- HTTP/1.1 endpoints containing object IDs like userID (e.g.
`/management/v1/users/2352839823/`)
- high amount of traces from internal processes (spooler)
- high cardinality in metrics endpoint:
  - GRPC entries containing host names
  - notification metrics containing instanceIDs and error messages

# How the Problems Are Solved

- Properly initialize the interceptors once and update them to use the
grpc stats handler (unary interceptors were deprecated).
- Remove host names from HTTP/1.1 span names and use path as default.
- Set / overwrite the uri for spans on the grpc-gateway with the uri
pattern (`/management/v1/users/{user_id}`). This is used for spans in
traces and metric entries.
- Created a new sampler which will only sample spans in the following
cases:
  - remote was already sampled
- remote was not sampled, root span is of kind `Server` and based on
fraction set in the runtime configuration
- This will prevent having a lot of spans from the spooler back ground
jobs if they were not started by a client call querying an object (e.g.
UserByID).
- Filter out host names and alike from OTEL generated metrics (using a
`view`).
- Removed instance and error messages from notification metrics.

# Additional Changes

Fixed the middleware handling for serving Console. Telemetry and
instance selection are only used for the environment.json, but not on
statically served files.

# Additional Context

- closes #8096
- relates to #9074
- back ports to at least 2.66.x, 2.67.x and 2.68.x

(cherry picked from commit 990e1982c7)

internal/telemetry/tracing/sampler.go

@@ -0,0 +1,46 @@
+package tracing
+
+import (
+	"fmt"
+	"slices"
+
+	sdk_trace "go.opentelemetry.io/otel/sdk/trace"
+	"go.opentelemetry.io/otel/trace"
+)
+
+type spanKindSampler struct {
+	sampler sdk_trace.Sampler
+	kinds   []trace.SpanKind
+}
+
+// ShouldSample implements the [sdk_trace.Sampler] interface.
+// It will not sample any spans which do not match the configured span kinds.
+// For spans which do match, the decorated sampler is used to make the sampling decision.
+func (sk spanKindSampler) ShouldSample(p sdk_trace.SamplingParameters) sdk_trace.SamplingResult {
+	psc := trace.SpanContextFromContext(p.ParentContext)
+	if !slices.Contains(sk.kinds, p.Kind) {
+		return sdk_trace.SamplingResult{
+			Decision:   sdk_trace.Drop,
+			Tracestate: psc.TraceState(),
+		}
+	}
+	s := sk.sampler.ShouldSample(p)
+	return s
+}
+
+func (sk spanKindSampler) Description() string {
+	return fmt.Sprintf("SpanKindBased{sampler:%s,kinds:%v}",
+		sk.sampler.Description(),
+		sk.kinds,
+	)
+}
+
+// SpanKindBased returns a sampler decorator which behaves differently, based on the kind of the span.
+// If the span kind does not match one of the configured kinds, it will not be sampled.
+// If the span kind matches, the decorated sampler is used to make sampling decision.
+func SpanKindBased(sampler sdk_trace.Sampler, kinds ...trace.SpanKind) sdk_trace.Sampler {
+	return spanKindSampler{
+		sampler: sampler,
+		kinds:   kinds,
+	}
+}