feat(sound): rebase with varlink sound settings API

[mmstick]

• Update to use the varlink sound settings API from the settings daemon.
• Drops the cosmic-pipewire crate that the settings daemon now manages
• Drops the pipewire and pulse subscriptions that will be deprecated by this
• Drops the libpipewire build dependency

Depends on pop-os/cosmic-settings-daemon#135 and pop-os/cosmic-applets#1352

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