This change was a fix for a latent bug from the vanity imports migration
but is unrelated to map support. Removing to keep the PR focused on Rust.

- Make `InterfaceGenerator::type_map` a required trait method instead of
  providing a default `todo!()` impl, so missing implementations are
  caught at compile time rather than runtime.
- Remove `RuntimeItem::MapType` indirection in the Rust backend; reference
  `{rt}::Map` directly instead of emitting a `pub use` re-export.
- Fix borrowed map rendering to use `&Map<K, V>` instead of the
  incorrect `&[(K, V)]` slice syntax that was copy-pasted from lists.
- Add explanatory comments on map ABI methods that reuse list
  read/write helpers (maps share the list<tuple<K, V>> memory layout).
- Add explicit `type_map` todo stubs to C, C++, C#, Go, and MoonBit
  backends.

- Make `anonymous_type_map` a required method on `AnonymousTypeGenerator`
  trait (no default impl), consistent with all other methods in the trait.
- Add explicit `anonymous_type_map` todo!() implementation to C backend.
- Fix map runner test to construct proper Map types instead of passing
  slice literals, matching the generated `&Map<K, V>` parameter signatures.

The map.wit codegen test hits todo!() panics in backends that don't yet
implement map support (C, C++, C#, Go, MoonBit). Add map.wit to each
backend's should_fail_verify so CI treats these as expected failures.

- Run cargo fmt to fix formatting in c/lib.rs, test/c.rs, test/moonbit.rs.
- Use starts_with("map.wit") for the C backend's should_fail_verify to
  catch all codegen test variants (no-sig-flattening, autodrop, async).

Signed-off-by: Yordis Prieto <yordis.prieto@gmail.com>

Exercise additional ABI code paths: nested map<K, map<K2, V>> with
recursive lower/lift blocks, multiple map parameters with independent
ptr/len pairs, map as a variant arm payload, map inside result<ok, err>,
and tuple-with-map in codegen.

Exercise map inside an anonymous tuple (filter_mode_preserve_top path)
and the single-entry boundary case.

Signed-off-by: Yordis Prieto <yordis.prieto@gmail.com>

- Unit tests for WitMap trait impls (BTreeMap, HashMap, reference blanket)
- Proc-macro integration tests exercising map_type with HashMap and default
- Codegen test variant running all .wit files with --map-type=HashMap

Remove `type Iter` and `wit_map_into_iter` from the `WitMap` trait and
drop the `IntoIterator` bound from the blanket `&T` impl. This allows
the blanket impl to apply at any reference depth (e.g. `&&BTreeMap`)
which is needed when codegen emits `WitMap::wit_map_len(&map)` on an
already-borrowed map.

Generated lowering code now uses `IntoIterator::into_iter(map)` for
iteration, which the standard library already provides for both owned
and borrowed map types.

Use method syntax (.wit_map_len() and .into_iter()) in generated
MapLower code instead of UFCS. This lets Rust's auto-deref handle
&&BTreeMap operands that arise when the borrow-mode param wrapper
adds an extra & prefix to already-borrowed map arguments.

A scoped `use WitMap;` import is emitted so method resolution finds
the trait's wit_map_len method.

Revert MapLower to use method syntax for length and iteration, matching
the original pre-WitMap code. Method syntax auto-derefs through &&Map
operands that arise in borrowed ownership modes.

Simplify WitMap trait to just new/push (used only in MapLift). The map
type must also provide .len() and implement IntoIterator, which all
standard map types already do.