Move notification FDs to config

[git-f0x]

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Moves the notification FDs to config, since util pulls in a lot of dependencies (and config seems like the better place for this). This prevents e.g. cosmic-session from pulling in 3000+ lines of Cargo.lock after a cargo update because of util (libcosmic), and instead it's only ~100.
Though I'm not sure if it's needed to pull in this crate just because of those 2 constants, and they're unlikely to change. Removing the dep from cosmic-session cuts over 400 lines in its Cargo.lock.

Updates dependencies and addresses clippy lints.

The last commit also removes the data and i18n folders, since a desktop file and placeholder icon don't seem to be needed for a notification daemon (it shows up in COSMIC Store), and localizations are unused.
Something similar should probably also be done for cosmic-bg.

[git-f0x]

Any logs for why this failed to build? It builds and vendors fine locally.

[mmstick]

just rootdir=debian/cosmic-notifications install
error: Justfile does not contain recipe `install`
make[1]: *** [debian/rules:31: override_dh_install] Error 1

[git-f0x]

Oh, whoops. 😅
Should be fixed now.