…0353)

Removes the `AstFactory` newtype (rolldown's wrapper over oxc's `AstBuilder`) and moves rolldown's recurring AST constructions onto per-node-type extension traits, matching oxc's own methods-on-types construction shape. Rolldown now holds and passes oxc's `AstBuilder` directly.

## What

- `AstFactory`'s ~28 inherent `make_*` methods become `new_*` associated functions on `*FactoryExt` traits — `ExpressionFactoryExt`, `StatementFactoryExt`, `MemberExpressionFactoryExt`, `CallExpressionFactoryExt`, `BindingIdentifierFactoryExt`, `IdentifierNameFactoryExt`, `ObjectPropertyKindFactoryExt`, `ClassElementFactoryExt` — each generic over `B: GetAstBuilder<'ast> + GetAllocator<'ast>` and taking the builder as its **last** argument (e.g. `Expression::new_id_ref_expr(SPAN, name, builder)`).
- `BindingPatternExt` / `BindingPropertyExt` are made generic over the builder the same way, decoupling them from the deleted type.
- Every holder struct's `ast_factory: AstFactory` field becomes `ast_builder: AstBuilder`; call sites go from `self.ast_factory.make_x(..)` to `Type::new_x(.., &self.ast_builder)`.
- `internal-docs/ast-construction/implementation.md` is updated to describe the new convention.

## Why

- **Matches oxc.** Construction lives on the AST types for both oxc and rolldown nodes, builder passed last.
- **Builder-last unblocks `&mut` construction.** Passing the builder as an argument rather than a `self` receiver is what lets oxc later switch builder methods to `&mut AstBuilder` — dropping the `Cell`s from `Allocator` (a hot-path win) and enabling stateful builders that auto-assign unique `NodeId`s.
- **Statefulness stays reintroducible.** Because every constructor is generic over the builder, a future stateful wrapper (`impl GetAstBuilder + GetAllocator`) can be threaded through with zero call-site changes.

## Notes vs the proposal

Two intentional differences from the sketch in the issue:

- Method names keep the operation suffix (`new_id_ref_expr`, not `new_id_ref`); the `new_*` names are operation-based (`new_keep_name_call`), disjoint from oxc's variant-based constructors (`new_call_expression`), so none collide.
- Holder structs keep an `ast_builder` field and pass `&self.ast_builder`, rather than implementing `GetAstBuilder` themselves to pass `self`. The borrow-check benefit still holds via argument evaluation order; the shorter `self` call syntax is a possible follow-up.

Closes #10328