User agent is getting replaced by client hints

[CendioOssman]

Browsers are moving to deprecate the user agent string in favour of a more flexible "client hints" system. As we currently do some checks based on user agent we need to keep up with these changes to avoid mis-detecting things.

https://wicg.github.io/ua-client-hints/
https://github.com/WICG/ua-client-hints
https://blog.chromium.org/2021/05/update-on-user-agent-string-reduction.html