Refactor Destructure to handle assignments

Renames `DefDestructure` to `Destructure` to better reflect its use in
both definitions and assignments.
Introduces `bind_assign_pattern` to handle assignment destructuring in
the binder.
Adds `test_assign_destructuring` to verify assignment destructuring
functionality.

src/ast/compiler/dumper.rs

@@ -120,8 +120,8 @@ impl Dumper {
                 self.indent -= 1;
             }
 
-            BoundKind::DefDestructure { pattern, value } => {
-                self.log("DefDestructure", node);
+            BoundKind::Destructure { pattern, value } => {
+                self.log("Destructure", node);
                 self.indent += 1;
                 self.write_indent();
                 self.output.push_str("Pattern:\n");