Descriptions for feature flag release conditions

[havenbarnes]

Feature request

Is your feature request related to a problem?

https://posthog.slack.com/archives/C07Q2U4BH4L/p1739458336401369

Describe the solution you'd like

Add description to release conditions so I can have multiple blocks with descriptions of what they are in the case it's just a bunch of ids.

Describe alternatives you've considered

There is no field to add context to a release condition today

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]