spanner: support custom meterprovider for builtin metrics

[tyrone-anz]

Is your feature request related to a problem? Please describe.

Spanner client is sending builtin/native metrics directly to GCP by default.

For services that have no permission, the metric export results to error log and span with following message.

Permission monitoring.timeSeries.create denied (or the resource may not exist).

For the above noise to go away, the native metrics can be disabled (SPANNER_DISABLE_BUILTIN_METRICS=true) or simply give service the missing permission. However, this is always something to keep in mind for a new service using spanner.

Describe the solution you'd like

Use the ClientConfig.OpenTelemetryMeterProvider from the config

Code affected.

google-cloud-go/spanner/client.go

Lines 496 to 511 in 5b59819

	var metricsProvider metric.MeterProvider
	if emulatorAddr := os.Getenv("SPANNER_EMULATOR_HOST"); emulatorAddr != "" {
	// Do not emit native metrics when emulator is being used
	metricsProvider = noop.NewMeterProvider()
	}
	// Check if native metrics are disabled via env.
	if disableNativeMetrics, _ := strconv.ParseBool(os.Getenv("SPANNER_DISABLE_BUILTIN_METRICS")); disableNativeMetrics {
	config.DisableNativeMetrics = true
	}
	if config.DisableNativeMetrics {
	// Do not emit native metrics when DisableNativeMetrics is set
	metricsProvider = noop.NewMeterProvider()
	}
	// Create a OpenTelemetry metrics configuration
	metricsTracerFactory, err := newBuiltinMetricsTracerFactory(ctx, database, metricsProvider)

Describe alternatives you've considered

• Allow a param that sends builtin metrics to the global meter provider otel.GetMeterProvider()

Additional context

Add any other context or screenshots about the feature request here.