cranelift-wasm: Create ModuleTranslationState and polish API a little (#1111)

* cranelift-wasm: replace `WasmTypesMap` with `ModuleTranslationState`

The `ModuleTranslationState` contains information decoded from the Wasm module
that must be referenced during each Wasm function's translation.

This is only for data that is maintained by `cranelift-wasm` itself, as opposed
to being maintained by the embedder. Data that is maintained by the embedder is
represented with `ModuleEnvironment`.

A `ModuleTranslationState` is returned by `translate_module`, and can then be
used when translating functions from that module.

* cranelift-wasm: rename `TranslationState` to `FuncTranslationState`

To disambiguate a bit with the new `ModuleTranslationState`.

* cranelift-wasm: Reorganize the internal `state` module into submodules

One module for the `ModuleTranslationState` and another for the
`FuncTranslationState`.

* cranelift-wasm: replace `FuncTranslator` with methods on `ModuleTranslationState`

`FuncTranslator` was two methods that always took ownership of `self`, so it
didn't really make sense as an object as opposed to two different functions, or
in this case methods on the object that actually persists for a longer time.

I think this improves ergonomics nicely.

Before:

```rust
let module_translation = translate_module(...)?;
for body in func_bodies {
    let mut translator = FuncTranslator::new();
    translator.translate(body, ...)?;
}
```

After:

```rust
let module_translation = translate_module(...)?;
for body in func_bodies {
    module_translation.translate_func(body, ...)?;
}
```

Note that this commit does not remove `FuncTranslator`. It still exists, but is
just a wrapper over the `ModuleTranslationState` methods, and it is marked
deprecated, so that downstream users get a heads up. This should make the
transition easier.

* Revert "cranelift-wasm: replace `FuncTranslator` with methods on `ModuleTranslationState`"

This reverts commit 075f9ae933bcaae39348b61287c8f78a4009340d.

cranelift/wasm/src/translation_utils.rs

@@ -1,5 +1,6 @@
 //! Helper functions and structures for the translation.
-use crate::environ::{WasmResult, WasmTypesMap};
+use crate::environ::WasmResult;
+use crate::state::ModuleTranslationState;
 use crate::wasm_unsupported;
 use core::u32;
 use cranelift_codegen::entity::entity_impl;
@@ -148,7 +149,7 @@ pub fn tabletype_to_type(ty: wasmparser::Type) -> WasmResult<Option<ir::Type>> {
 
 /// Get the parameter and result types for the given Wasm blocktype.
 pub fn blocktype_params_results(
-    wasm_types: &WasmTypesMap,
+    module_translation_state: &ModuleTranslationState,
     ty_or_ft: wasmparser::TypeOrFuncType,
 ) -> WasmResult<(&[wasmparser::Type], &[wasmparser::Type])> {
     Ok(match ty_or_ft {
@@ -163,7 +164,7 @@ pub fn blocktype_params_results(
         },
         wasmparser::TypeOrFuncType::FuncType(ty_index) => {
             let sig_idx = SignatureIndex::from_u32(ty_index);
-            let (ref params, ref returns) = wasm_types.inner[sig_idx];
+            let (ref params, ref returns) = module_translation_state.wasm_types[sig_idx];
             (&*params, &*returns)
         }
     })