[RFC]: support of new Talk features in Desktop with old servers

[Antreesy]

Features a-like this one (pure frontend, server is only needed for cross-device support) e.g.:

• call without media Add option for camera and mic to be disabled by default spreed#13446
• blur background feat(call): add option to enable blur background by default for all c… spreed#13490
• compact conversations list Conversations list compact mode spreed#11697

can be supported with Desktop client with old servers, but keep it in BrowserStorage instead of sending a request to backend

Originally posted by @Antreesy in #957

[nickvergessen]

This is not completed?
Or did you patch anything here or in spreed?