Format .nix files

This does not include any automation for the release branch, but
is based on the configuration of https://github.com/NixOS/nix/pull/12349

    pre-commit run -a nixfmt-rfc-style

src/internal-api-docs/package.nix

@@ -1,11 +1,12 @@
-{ lib
-, mkMesonDerivation
+{
+  lib,
+  mkMesonDerivation,
 
-, doxygen
+  doxygen,
 
-# Configuration Options
+  # Configuration Options
 
-, version
+  version,
 }:
 
 let
@@ -17,27 +18,28 @@ mkMesonDerivation (finalAttrs: {
   inherit version;
 
   workDir = ./.;
-  fileset = let
-    cpp = fileset.fileFilter (file: file.hasExt "cc" || file.hasExt "hh");
-  in fileset.unions [
-    ./.version
-    ../../.version
-    ./meson.build
-    ./doxygen.cfg.in
-    # Source is not compiled, but still must be available for Doxygen
-    # to gather comments.
-    (cpp ../.)
-  ];
+  fileset =
+    let
+      cpp = fileset.fileFilter (file: file.hasExt "cc" || file.hasExt "hh");
+    in
+    fileset.unions [
+      ./.version
+      ../../.version
+      ./meson.build
+      ./doxygen.cfg.in
+      # Source is not compiled, but still must be available for Doxygen
+      # to gather comments.
+      (cpp ../.)
+    ];
 
   nativeBuildInputs = [
     doxygen
   ];
 
-  preConfigure =
-    ''
-      chmod u+w ./.version
-      echo ${finalAttrs.version} > ./.version
-    '';
+  preConfigure = ''
+    chmod u+w ./.version
+    echo ${finalAttrs.version} > ./.version
+  '';
 
   postInstall = ''
     mkdir -p ''${!outputDoc}/nix-support