chore: rebrand Nix to Lix when it makes sense

Here's my guide so far:

$ rg '((?!(recursive).*) Nix
(?!(daemon|store|expression|Rocks!|Packages|language|derivation|archive|account|user|sandbox|flake).*))'
-g '!doc/' --pcre2

All items from this query have been tackled. For the documentation side:
that's for https://git.lix.systems/lix-project/lix/issues/162.

Additionally, all remaining references to github.com/NixOS/nix which
were not relevant were also replaced.

Fixes: https://git.lix.systems/lix-project/lix/issues/148.
Fixes: https://git.lix.systems/lix-project/lix/issues/162.
Change-Id: Ib3451fae5cb8ab8cd9ac9e4e4551284ee6794545
Signed-off-by: Raito Bezarius <raito@lix.systems>

src/libexpr/eval-settings.hh

@@ -71,8 +71,8 @@ struct EvalSettings : Config
     Setting<bool> enableImportFromDerivation{
         this, true, "allow-import-from-derivation",
         R"(
-          By default, Nix allows you to `import` from a derivation, allowing
-          building at evaluation time. With this option set to false, Nix will
+          By default, Lix allows you to `import` from a derivation, allowing
+          building at evaluation time. With this option set to false, Lix will
           throw an error when evaluating an expression that uses this feature,
           allowing users to ensure their evaluation will not require any
           builds to take place.