Add tenant id attribute to default tracer about grafana-plugin-sdk-go

[xnyo]

The plugin runner already includes a stackID attribute in its queryData span:

I am not sure if adding the stack id to the resource attributes makes sense, as those should be for information about the running process/environment, not the request:

https://opentelemetry.io/docs/instrumentation/go/resources/

POC PR #769 implements adding it as a span attribute instead, but that would include the stackID/tenant_id in all spans that are created by the plugin via tracing.DefaultTracer():

(tenant_id is added automatically):

	ctx, span := tracing.DefaultTracer().Start(
		ctx,
		"query processing",
		trace.WithAttributes(
			attribute.String("query.ref_id", query.RefID),
			attribute.String("query.type", query.QueryType),
			attribute.Int64("query.max_data_points", query.MaxDataPoints),
			attribute.Int64("query.interval_ms", query.Interval.Milliseconds()),
			attribute.Int64("query.time_range.from", query.TimeRange.From.Unix()),
			attribute.Int64("query.time_range.to", query.TimeRange.To.Unix()),
		),
	)
	defer span.End()

[marefr]

@xnyo fixed by #769 ?

[xnyo]

closing as fixed by #769