Remember whether sidebar is shown for calls when switching rooms

[bojidar-bg]

Stores the sidebar state per-room in LegacyCallHandler, where other details about calls are already stored.

Fixes #25367.

Checklist

• 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.

[dbkr]

Thanks for this! The code looks straightforward enough. Just one minor lint error. A new feature would need test coverage though.

[bojidar-bg]

Huh. I'm this sure I ran the linter, guess I didn't 😂

Should I make the test in test/unit-tests/components/views/voip/LegacyCallView-test.tsx? Or would something around playwright/e2e/voip be advisable? Just making sure, as I didn't see other tests covering the rest of LegacyCallView's features to go off of (:

[bojidar-bg]

BTW, this PR was made as part of a live stream/speedrun (: You can see the final demonstration of the feature working at 2:10:28 - and yes, I did run the linter at 1:29:16, but then I never ran it on the PIP changes 😂
(just a shamless plug 😇)

[dbkr]

Oh, nice! I'd probably do a jest test in LegacyCallView-test.tsx as it should be quite simple to assert that the dom element is there. There's probably no need to make it a playwright test.

Also reminder not to force push PRs please, it means we lose the record of what code has been reviewed.

[bojidar-bg]

Alright, added a test (: