Remove getNativeFieldSize build-time helper. NFC (#19258)

This function had exactly one callsite, where its wasn't serving any
useful purpose:

```
if (!WASM_BIGINT && getNativeFieldSize(type) > 4 && type == 'i64') {
```

Here the second clause in the condition would always return true when
`type` in `i64` making the redundant in the face the third clause.  This
is because `getNativeFieldSize('i64')` always returns 8.

Author: sbc100

src/parseTools.js

@@ -258,8 +258,9 @@ function indentify(text, indent) {
 // Correction tools
 
 function getHeapOffset(offset, type) {
-  if (!WASM_BIGINT && getNativeFieldSize(type) > 4 && type == 'i64') {
-    // we emulate 64-bit integer values as 32 in asmjs-unknown-emscripten, but not double
+  if (type == 'i64' && !WASM_BIGINT) {
+    // We are foreced to use the 32-bit heap for 64-bit values when we don't
+    // have WASM_BIGINT.
     type = 'i32';
   }
 

src/parseTools_legacy.js

@@ -89,6 +89,10 @@ function makeMalloc(source, param) {
   return `_malloc(${param})`;
 }
 
+function getNativeFieldSize(type) {
+  return Math.max(getNativeTypeSize(type), POINTER_SIZE);
+}
+
 global.Runtime = {
   getNativeTypeSize: getNativeTypeSize,
   getNativeFieldSize: getNativeFieldSize,

src/runtime.js

@@ -33,7 +33,3 @@ function getNativeTypeSize(type) {
     }
   }
 }
-
-function getNativeFieldSize(type) {
-  return Math.max(getNativeTypeSize(type), POINTER_SIZE);
-}