feat: Implement AST macros and templates

This commit introduces support for AST macros and templates, enabling
users to define and use custom, reusable components within the visual
DSL.

Key changes include:
- A new `MacroRegistry` to manage macro definitions.
- A `MacroExpander` to process macro calls and expand templates.
- A `MacroEvaluator` trait for evaluating expressions during expansion.
- The `Expansion` node in `BoundKind` to preserve the original macro
  call and its expanded form for debugging.
- Updates to the `Binder`, `Dumper`, and `UpvalueAnalyzer` to handle the
  new macro constructs.
- New examples demonstrating various macro functionalities like
  `unless`, splicing, and nested macros.

src/ast/compiler/dumper.rs

@@ -149,6 +149,13 @@ impl Dumper {
                 }
                 self.indent -= 1;
             }
+
+            BoundKind::Expansion { original_call, bound_expanded } => {
+                self.log(&format!("Expansion (Original: {:?})", original_call.kind), node);
+                self.indent += 1;
+                self.visit(bound_expanded);
+                self.indent -= 1;
+            }
         }
     }
 }