healthcheckextension: Add an ability to delay collector shutdown

[yuri-rs]

Component(s)

extension/healthcheck, extension/healthcheckv2

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

We have a problem with 503 errors in the K8s environment for the otel endpoint.
These errors occur during the distribution/change of the collector configuration.
We have a process to restart the collector inside the pod with the new configuration.
During the configuration rollout, the collector shuts down too quickly, so K8s doesn't update the pod's healthy state and continues sending requests to this pod, leading to 503 errors.

Describe the solution you'd like

I'd like to have a way to delay the collector/endpoint shutdown after the HC state changes to NotReady.
This way, pod readiness would catch the NotReady status and move the traffic to the other pods before the actual collector shutdown.

It could look like: yuri-rs@55e0c5a

Describe alternatives you've considered

An alternative could be a delay in the collector service itself, like (added sleep line):

// Shutdown the service. Shutdown will do the following steps in order:
// 1. Notify extensions that the pipeline is shutting down.
// 2. Shutdown all pipelines.
// 3. Shutdown all extensions.
// 4. Shutdown telemetry.
func (srv *Service) Shutdown(ctx context.Context) error {
	// Accumulate errors and proceed with shutting down remaining components.
	var errs error

	// Begin shutdown sequence.
	srv.telemetrySettings.Logger.Info("Starting shutdown...")

	if err := srv.host.serviceExtensions.NotifyPipelineNotReady(); err != nil {
		errs = multierr.Append(errs, fmt.Errorf("failed to notify that pipeline is not ready: %w", err))
	}
	
	time.Sleep(time.Second)

	if err := srv.host.pipelines.ShutdownAll(ctx, srv.reporter); err != nil {
		errs = multierr.Append(errs, fmt.Errorf("failed to shutdown pipelines: %w", err))
	}

However, doing it inside the healthcheck extension seems better to me.

Additional context

What do you think about this feature?
Would you accept a PR with this functionality?

[github-actions]

Pinging code owners:

• extension/healthcheck: @jpkrohling
• extension/healthcheckv2: @jpkrohling @mwear

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[jpkrohling]

The current health check extension will give way to the health check v2 extension, which should be ready soon. @mwear, do you remember if this use-case is part of the scope for v2 already?