Make upgrading OpenTelemetry easier (#7712)

OpenTelemetry has "semantic conventions" which are versioned
independently of the software package, as it describes the semantics of
the resources being produced. Previously, we'd combined
`resource.Default()` using the `Merge` function with our own resources.

Merge, however, doesn't handle merging resources with different semantic
conventions. This means that every dependabot PR that bumps otel will
break when the `resources.Default` has a new version.

That doesn't seem worth it for the default resources, so just provide
our own resources which have everything we care about. I've added the
PID which we didn't have before but will be interesting. We will lose
the SDK's version, but I don't think that matters.

For more discussion on this topic, see
https://github.com/open-telemetry/opentelemetry-go/issues/3769

cmd/shell.go

@@ -314,20 +314,15 @@ func NewOpenTelemetry(config OpenTelemetryConfig, logger blog.Logger) func(ctx c
 	otel.SetLogger(stdr.New(logOutput{logger}))
 	otel.SetErrorHandler(otel.ErrorHandlerFunc(func(err error) { logger.Errf("OpenTelemetry error: %v", err) }))
 
-	r, err := resource.Merge(
-		resource.Default(),
-		resource.NewWithAttributes(
-			semconv.SchemaURL,
-			semconv.ServiceNameKey.String(core.Command()),
-			semconv.ServiceVersionKey.String(core.GetBuildID()),
-		),
+	resources := resource.NewWithAttributes(
+		semconv.SchemaURL,
+		semconv.ServiceName(core.Command()),
+		semconv.ServiceVersion(core.GetBuildID()),
+		semconv.ProcessPID(os.Getpid()),
 	)
-	if err != nil {
-		FailOnError(err, "Could not create OpenTelemetry resource")
-	}
 
 	opts := []trace.TracerProviderOption{
-		trace.WithResource(r),
+		trace.WithResource(resources),
 		// Use a ParentBased sampler to respect the sample decisions on incoming
 		// traces, and TraceIDRatioBased to randomly sample new traces.
 		trace.WithSampler(trace.ParentBased(trace.TraceIDRatioBased(config.SampleRatio))),