Feature Request: Support time to convert in funnel metrics

Feature request

Is your feature request related to a problem?

The insight we display for funnel type experiment metrics does not show 'time to convert'.

Describe the solution you'd like

Report time to convert for experiment funnel metrics.

Describe alternatives you've considered

Reconstruct the funnel in PostHog analytics, bearing in mind that conversion numbers may not match perfectly.

Additional context

From: https://posthoghelp.zendesk.com/agent/tickets/39571 (moved to PostHog: https://us.posthog.com/project/2/support/tickets/41776)

Debug info

Kind: bug

Target area: experiments

Report event: http://go/ticketByUUID/56558122-7512-4df8-bb02-c1b66a1c69b9

Session: https://us.posthog.com/project/sTMFPsFhdP1Ssg/replay/0199c46b-9022-7f67-9bbb-497804a85ed9?t=9440

Exceptions: https://us.posthog.com/project/2/error_tracking?filterGroup=%7B%22type%22%3A%22AND%22%2C%22values%22%3A%5B%7B%22type%22%3A%22AND%22%2C%22values%22%3A%5B%7B%22key%22%3A%22%24session_id%22%2C%22value%22%3A%5B%220199c46b-9022-7f67-9bbb-497804a85ed9%22%5D%2C%22operator%22%3A%22exact%22%2C%22type%22%3A%22event%22%7D%5D%7D%5D%7D

Location: https://us.posthog.com/project/51935

Persons-on-events mode for project: person_id_override_properties_joined

The issue does not name files, tests, or entry points. Start by locating the experiment funnel metrics implementation and its existing insight calculations; compare the result with the PostHog analytics funnel, then define completion as reporting time to convert for experiment funnel metrics with coverage for the relevant metric behavior.