Feature Request: Allow setting a display name for feature flags

Feature request

Is your feature request related to a problem?

• Right now feature flags only allow you to set a slug, and not a simple display name.
• You aren't easily able to change the slug name, because this would affect your feature flag calls and you'd have to perform code changes to handle the new slug.
• This becomes problematic over time as features you've built change.
• For example, if your feature flag is called feature-a-beta during a beta test, you're stuck using that same slug once the feature moves out from beta to general access.

Describe the solution you'd like

• It would be great to have a display name in addition to a slug.
• Users should be able to adjust the display name at any time.

Describe alternatives you've considered

• At the moment we do have a Description displayed in the UI that people can use for their descriptors.
  • However, this is a less prominent field which is harder to easily read at a glance.
  • This is even called the Name field in the API.

Additional context

• From https://posthoghelp.zendesk.com/agent/tickets/55062 (moved to PostHog: https://us.posthog.com/project/2/support/tickets/55936)

Debug info

Session: https://us.posthog.com/project/sTMFPsFhdP1Ssg/replay/019d5451-afe4-7a50-b6a8-bf537f564f38?t=10136
Admin: http://go/adminOrgUS/019c4ed6-add0-0000-998a-30c999608349 (project ID 311650)

The issue names no files, tests, or entry points. Start by tracing the feature-flag model/API and its UI representation, including how the existing slug and Description/Name fields are stored and displayed. Done means users can edit a separate display name without changing the slug or flag calls, with the relevant behavior covered by tests.