use lib.makeScope and files to organize packages

Some of the improvements here include:

* rocksdb can actually use jemalloc now instead of just pulling in a
  second rocksdb for no reason
* "complement-runtime" factored back out into shell file
* complement image no longer uses `mkDerivation` for `copyToRoot`
  because that's what `buildEnv` is for
* complement image no longer sets `SERVER_NAME`, complement already does
  that
* all packages were factored out into `callPackage`-able files for use
  with a custom `lib.makeScope pkgs.newScope`
* new version of `mkPackage` has options that are easier to use and
  override such as `features`

nix/pkgs/book/default.nix

@@ -0,0 +1,31 @@
+{ inputs
+
+# Dependencies
+, main
+, mdbook
+, stdenv
+}:
+
+stdenv.mkDerivation {
+  inherit (main) pname version;
+
+  src = inputs.nix-filter {
+    root = inputs.self;
+    include = [
+      "book.toml"
+      "conduwuit-example.toml"
+      "README.md"
+      "debian/README.md"
+      "docs"
+    ];
+  };
+
+  nativeBuildInputs = [
+    mdbook
+  ];
+
+  buildPhase = ''
+    mdbook build
+    mv public $out
+  '';
+}