* remove libsystemd dependency
as per Lennart Poettering's advice:
https://github.com/systemd/systemd/issues/32028#issuecomment-2031366922
* fix naming for systemd helper functions
* rename vars according to code style
* Nix: update meson patch
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Co-authored-by: Mihai Fufezan <mihai@fufexan.net>
