Non-functional. Rationalizations enabling future generalizations:

- Use much simpler method to update implicit array sizes.
  The previous overly complicated method was error prone.
- Rationalize all use of unsized arrays.
- Combine decorations when generating SPIR-V, to simplify
  adding extensions.

hlsl/hlslGrammar.cpp

@@ -2569,8 +2569,8 @@ bool HlslGrammar::acceptParameterDeclaration(TFunction& function)
     TArraySizes* arraySizes = nullptr;
     acceptArraySpecifier(arraySizes);
     if (arraySizes) {
-        if (arraySizes->isImplicit()) {
-            parseContext.error(token.loc, "function parameter array cannot be implicitly sized", "", "");
+        if (arraySizes->hasUnsized()) {
+            parseContext.error(token.loc, "function parameter requires array size", "[]", "");
             return false;
         }