Combine VisibleTranslationState and TranslationState (#1076)

`VisibleTranslationState` was a wrapper around a `TranslationState` that was
meant to public API consumers outside of this crate. However, the internal
`TranslationState` and all its methods were still publicly exposed! This commit
simplifies and remedies the situation by combining them into a single
`TranslationState` type. Most of its methods are only `pub(crate)` now, not
visible to the entire world. The only methods that are `pub` are the ones that
`VisibleTranslationState` exposed.

cranelift/wasm/src/environ/spec.rs

@@ -6,7 +6,7 @@
 //!
 //! [Wasmtime]: https://github.com/CraneStation/wasmtime
 
-use crate::state::VisibleTranslationState;
+use crate::state::TranslationState;
 use crate::translation_utils::{
     FuncIndex, Global, GlobalIndex, Memory, MemoryIndex, SignatureIndex, Table, TableIndex,
 };
@@ -281,7 +281,7 @@ pub trait FuncEnvironment {
         &mut self,
         _op: &Operator,
         _builder: &mut FunctionBuilder,
-        _state: &VisibleTranslationState,
+        _state: &TranslationState,
     ) -> WasmResult<()> {
         Ok(())
     }
@@ -292,7 +292,7 @@ pub trait FuncEnvironment {
         &mut self,
         _op: &Operator,
         _builder: &mut FunctionBuilder,
-        _state: &VisibleTranslationState,
+        _state: &TranslationState,
     ) -> WasmResult<()> {
         Ok(())
     }