chore(buildClan): rename eval.nix to function-adapter.nix to make its shallows purpose more clear

lib/build-clan/function-adapter.nix

@@ -0,0 +1,21 @@
+{
+  lib,
+  nixpkgs,
+  clan-core,
+  self,
+  specialArgs ? { },
+}:
+# Returns a function that takes self, which should point to the directory of the flake
+module:
+(lib.evalModules {
+  specialArgs = {
+    inherit self clan-core nixpkgs;
+  };
+  modules = [
+    ./interface.nix
+    module
+    {
+      inherit specialArgs;
+    }
+  ];
+}).config