Organizations release process (2/2): release status table and dev guide

What does this MR do?

Part 2 of 2 of the Organizations release process. Stacked on !239926 (merged) — this MR targets that MR's branch, so review/merge !239926 (merged) first. GitLab retargets this MR to master once !239926 (merged) merges.

Adds the documentation and tooling on top of the release layer:

• Organizations::Release::TableRenderer and a rake task (gitlab:organizations:release:docs) that generate a per-capability release status table from the registry.
• The generated doc/development/organizations/release_status.md, kept in sync by a gitlab:organizations:release:check_docs task run in the existing docs-lint generated-content CI job (the same job that checks the event store docs). It fails the pipeline if the registry changes without regenerating the doc.
• A developer guide doc/development/organizations/release_process.md that defers to the handbook for the model and covers the in-repo specifics (the layer, declaring a capability, operating the stage flags).

Why a repo doc as well as the handbook

The release model lives in the handbook (gitlab-com/content-sites/handbook!20007 (merged)). This repo doc is the developer implementation guide for engineers working in this codebase, and the status table is generated from the in-repo registry — so both belong here, pointing at the handbook for the model rather than duplicating it.

Status

Not wired into anything yet.

Example of the generated table

The committed release_status.md stays empty until a feature adopts the layer. With four illustrative flags registered across stages, bin/rake gitlab:organizations:release:docs generates this ## Organization flags section:

Example generated table

Flag	Stage	Description
organization_switching	Experimental	Switch the active organization from the UI.
ui_for_organizations	Beta	Browse and manage an organization through its dedicated UI.
organization_billing	LA (50%)	Manage billing at the organization level.
organization_activity	GA	Show an activity feed for the organization.

Rows are sorted by stage order, then name. The example flags above are illustrative and are not committed.