Fix high bits stored in uint64 representation of Word

Without first converting to uint32_t, the getters for wasm_val_t for
wamr, wasmtime, and wasmedge returned a signed integer type. For uint32
values high enough to be in the negative range, sign extension would be
applied when the value was coerced into proxy_wasm::Word. This resulted
in Word values that did not match the comment on Word

```
// Represents a Wasm-native word-sized datum. On 32-bit VMs, the high bits are always zero.
// The Wasm/VM API treats all bits as significant.
```

nor the exact value returned from the wasm plugin.

Signed-off-by: Matt Leon <mattleon@google.com>

Author: leonm1

src/wamr/wamr.cc

@@ -489,18 +489,21 @@ template <> auto convertArgToValTypePtr<Word>() { return wasm_valtype_new_i32();
 template <> auto convertArgToValTypePtr<uint32_t>() { return wasm_valtype_new_i32(); };
 template <> auto convertArgToValTypePtr<int64_t>() { return wasm_valtype_new_i64(); };
 template <> auto convertArgToValTypePtr<uint64_t>() { return wasm_valtype_new_i64(); };
-template <> auto convertArgToValTypePtr<double>() { return wasm_valtype_new_f64(); };
 template <> auto convertArgToValTypePtr<float>() { return wasm_valtype_new_f32(); };
+template <> auto convertArgToValTypePtr<double>() { return wasm_valtype_new_f64(); };
 
 template <typename T> T convertValueTypeToArg(wasm_val_t val);
 template <> uint32_t convertValueTypeToArg<uint32_t>(wasm_val_t val) {
   return static_cast<uint32_t>(val.of.i32);
 }
-template <> Word convertValueTypeToArg<Word>(wasm_val_t val) { return val.of.i32; }
+template <> Word convertValueTypeToArg<Word>(wasm_val_t val) {
+  return std::bit_cast<uint32_t>(val.of.i32);
+}
 template <> int64_t convertValueTypeToArg<int64_t>(wasm_val_t val) { return val.of.i64; }
 template <> uint64_t convertValueTypeToArg<uint64_t>(wasm_val_t val) {
   return static_cast<uint64_t>(val.of.i64);
 }
+template <> float convertValueTypeToArg<float>(wasm_val_t val) { return val.of.f32; }
 template <> double convertValueTypeToArg<double>(wasm_val_t val) { return val.of.f64; }
 
 template <typename T, typename U, std::size_t... I>

src/wasmedge/wasmedge.cc

@@ -152,13 +152,16 @@ template <typename T> T convValTypeToArg(WasmEdge_Value val);
 template <> uint32_t convValTypeToArg<uint32_t>(WasmEdge_Value val) {
   return static_cast<uint32_t>(WasmEdge_ValueGetI32(val));
 }
-template <> Word convValTypeToArg<Word>(WasmEdge_Value val) { return WasmEdge_ValueGetI32(val); }
+template <> Word convValTypeToArg<Word>(WasmEdge_Value val) {
+  return std::bit_cast<uint32_t>(WasmEdge_ValueGetI32(val));
+}
 template <> int64_t convValTypeToArg<int64_t>(WasmEdge_Value val) {
   return WasmEdge_ValueGetI64(val);
 }
 template <> uint64_t convValTypeToArg<uint64_t>(WasmEdge_Value val) {
   return static_cast<uint64_t>(WasmEdge_ValueGetI64(val));
 }
+template <> float convValTypeToArg<float>(WasmEdge_Value val) { return WasmEdge_ValueGetF32(val); }
 template <> double convValTypeToArg<double>(WasmEdge_Value val) {
   return WasmEdge_ValueGetF64(val);
 }

src/wasmtime/wasmtime.cc

@@ -469,7 +469,9 @@ template <typename T> T convertValueTypeToArg(wasm_val_t val);
 template <> uint32_t convertValueTypeToArg<uint32_t>(wasm_val_t val) {
   return static_cast<uint32_t>(val.of.i32);
 }
-template <> Word convertValueTypeToArg<Word>(wasm_val_t val) { return val.of.i32; }
+template <> Word convertValueTypeToArg<Word>(wasm_val_t val) {
+  return std::bit_cast<uint32_t>(val.of.i32);
+}
 template <> int64_t convertValueTypeToArg<int64_t>(wasm_val_t val) { return val.of.i64; }
 template <> uint64_t convertValueTypeToArg<uint64_t>(wasm_val_t val) {
   return static_cast<uint64_t>(val.of.i64);