This change converts redundant attribute assignments of the form `a =
a;` or `a = someSet.a;` into cleaner `inherit` statements. This reduces
verbosity and follows common Nix style for bringing attributes into
scope.
Statix Codes: W03 (manual_inherit), W04 (manual_inherit_from)
Also include statix and the rule in our configuration.
These were removed as part of dead code removal, but they are actually
needed in the integration tests for comparing with the configuration
generated by the installation.
currently ./format does a bunch of stuff with git that was only necessary for nixfmt but not nixfmt-tree, so I deleted it (just use treefmt command directly instead). I also added keep sorted to keep the really long module lists sorted (already used in nixpkgs).
