[receiver/kafka] Use proper context for shutdown

[djaglowski]

The background context was being used to manage a shutdown routine, which means that it will never shut down. This change just uses the correct context, which is passed to Start.

Resolves #30789 again

[crobert-1]

Suggested change

	func (c *kafkaTracesConsumer) Start(ctx context.Context, host component.Host) error {
	ctx, c.cancelConsumeLoop = context.WithCancel(ctx)
	func (c *kafkaTracesConsumer) Start(ctx context.Context, host component.Host) error {
	ctx, c.cancelConsumeLoop = context.WithCancel(ctx)

I don't think this is the solution here, as it goes against the spec's comments on context usage for components. The comment about Start here says we shouldn't use the passed in context for long-running background operations. At the moment using the passed in context doesn't cause any issues, but we don't want to go against the spec unless there's good reason.

Also, I don't believe this will resolve any kind of stuck shutdown. context.WithCancel creates a child context that can be cancelled independently of the parent. If the parent is shutdown, the child will automatically be shutdown as well, but there's no requirement vice versa. (The child can be shutdown just fine even if the parent is still running.)

I think there's else going on here, but feel free to correct me if I'm missing something here, or if you tested and confirmed this resolved the issue 🙂

[djaglowski]

You're right. Good explanation. I clearly didn't think this through very well.

[djaglowski]

Closing the PR in light of @crobert-1's point.