Feature request: Profiling backend server application (tracing, spans, flame graphs)

Feature request

Is your feature request related to a problem?

I would like to profile the performance of my nodejs backend application. For this I need to be able to trace when functions have been called and when they returned.

Describe the solution you'd like

Maybe by adding explicit posthog.captureSpanStart and posthog.captureSpanEnd calls to my code, that can be used to generate flame graphs from. But something more automagical that can be enabled once for my whole code base would be even better.

Describe alternatives you've considered

Sentry: https://docs.sentry.io/product/explore/profiling/flame-charts-graphs/

Additional context

Debug info

- [ ] PostHog Cloud, Debug information: [please copy/paste from https://us.posthog.com/settings/project-details#variables]
- [ ] PostHog Hobby self-hosted with `docker compose`, version/commit: [please provide]
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]

The issue names no repository files, tests, or entry points. Start by scoping how PostHog's Node.js backend application support could expose function tracing, spans, and flame graphs, using the linked Sentry profiling page as the stated comparison. Done should be a decided implementation scope rather than the current open-ended request.