Implement unstable support for MSC4472

[timedoutuk]

Implements special handling for deprecated room types, presenting a marginally different warning banner when a deprecated room type is in use (uses "end-of-life" for deprecated rooms instead of blanket "unstable")

Depends on matrix-org/matrix-js-sdk#5326

Note that while the i18n templates have all been updated, the English words end-of-life and unstable are now constants. Unfortunately I am unable to reliably translate these terms into all of the supported languages.

Checklist

• I have read through review guidelines and CONTRIBUTING.md.
• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• I have licensed the changes to Element by completing the Contributor License Agreement (CLA)

[CLAassistant]

All committers have signed the CLA.

[Half-Shot]

Couple of things to get you started

[Half-Shot]

So this is a rule that trips everyone up, but we don't edit non-english translations in PRs. You just edit en_EN.json and folks will kindly update the other translations through Localazy.

[timedoutuk]

Oh, fantastic

[Half-Shot]

A playwright test would be good to see this in action! https://github.com/element-hq/element-web/blob/develop/apps/web/playwright/e2e/room/room-status-bar.spec.ts#L29 is probably a good starting point. I would create a new test file for room upgrades, mock out the capabilities response to contain your new field, create a room with a deprecated version, and test that the banner appears.

Thanks!