feat(telemetry): auto detect google attributes (#12694)

# Which Problems Are Solved

We run multiple deployments (regions) under a single GCP project. Within
these deployments we scale containers. Currently all metrics target the
same time series in GCP, regardless or region or container. All metics
ended up in `generic_node` and Cloud Monitoring rejects the duplicate
and out-of-order points.

This can be fixed by setting vendor specific attributes such as
`faas.name` (K_SERVICE), `faas.version` (K_REVISION), `faas.instance`
(instance id from the metadata server), and `cloud.region` (metadata
instance/region).


# How the Problems Are Solved

Use `go.opentelemetry.io/contrib/detectors/gcp` to auto-detect values as
mentioned above. A new `Instrumentation.Detectors` config entry is
added, which accepts and array of enum for detecotrs. At the moment only
Google is accepted, other entries from
[contrib](https://github.com/open-telemetry/opentelemetry-go-contrib/tree/main/detectors)
can be added if deemed usefull.

I've considered using `autodetect` contrib package, identifiers and
constructor, but this pulls in the full AWS SDK, increasing zitadel's
binary size by 50MiB.

By default detection is switched off, as it relies on unauthenticated
link-local calls that are insecure anywhere outside of the
infrastructure it targets. It also prevents breaking existing
deployments that rely on detection being off already. (May break
existing trace and logging pipelines).

# Additional Changes

- none

# Additional Context

- (internal only): https://github.com/caos/infra/pull/1813

---------

Co-authored-by: Copilot Autofix powered by AI <[email protected]>
Co-authored-by: Claude Opus 5 <[email protected]>

go.mod

@@ -106,6 +106,7 @@ require (
 	github.com/zitadel/schema v1.3.2
 	github.com/zitadel/sloggcp v0.6.0
 	go.opentelemetry.io/contrib/bridges/otelslog v0.18.0
+	go.opentelemetry.io/contrib/detectors/gcp v1.44.0
 	go.opentelemetry.io/contrib/exporters/autoexport v0.68.0
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.68.0
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.68.0
@@ -259,7 +260,6 @@ require (
 	github.com/yuin/gopher-lua v1.1.2 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/contrib/bridges/prometheus v0.68.0 // indirect
-	go.opentelemetry.io/contrib/detectors/gcp v1.44.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.43.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.10.0 // indirect
 	go.uber.org/atomic v1.11.0 // indirect