Revert "LibJS: Get rid of unnecessary work from canonical_numeric_index_string"

This reverts commit 3a184f7841.

This broke a number of test262 tests under "TypedArrayConstructors".
The issue is that the CanonicalNumericIndexString AO should not fail
for inputs like "1.1", despite them not being integral indices.

Userland/Libraries/LibWeb/Bindings/IDLAbstractOperations.cpp

@@ -17,25 +17,39 @@
 namespace Web::Bindings::IDL {
 
 // https://webidl.spec.whatwg.org/#is-an-array-index
-bool is_an_array_index(JS::PropertyKey const& property_name)
+bool is_an_array_index(JS::GlobalObject& global_object, JS::PropertyKey const& property_name)
 {
     // 1. If Type(P) is not String, then return false.
     if (!property_name.is_number())
         return false;
 
     // 2. Let index be ! CanonicalNumericIndexString(P).
-    auto index = JS::canonical_numeric_index_string(property_name);
+    auto index = JS::canonical_numeric_index_string(global_object, property_name);
 
-    if (!index.has_value()) {
-        // All of these are handled by canonical_numeric_index_string
-        // 3. If index is undefined, then return false.
-        // 4. If IsInteger(index) is false, then return false.
-        // 5. If index is −0, then return false.
-        // 6. If index < 0, then return false.
-        // 7. If index ≥ 2 ** 32 − 1, then return false.
-        // Note: 2 ** 32 − 1 is the maximum array length allowed by ECMAScript.
+    // 3. If index is undefined, then return false.
+    if (index.is_undefined())
+        return false;
+
+    // 4. If IsInteger(index) is false, then return false.
+    // NOTE: IsInteger is the old name of IsIntegralNumber.
+    if (!index.is_integral_number())
+        return false;
+
+    // 5. If index is −0, then return false.
+    if (index.is_negative_zero())
+        return false;
+
+    // FIXME: I'm not sure if this is correct.
+    auto index_as_double = index.as_double();
+
+    // 6. If index < 0, then return false.
+    if (index_as_double < 0)
+        return false;
+
+    // 7. If index ≥ 2 ** 32 − 1, then return false.
+    // Note: 2 ** 32 − 1 is the maximum array length allowed by ECMAScript.
+    if (index_as_double >= NumericLimits<u32>::max())
         return false;
-    }
 
     // 8. Return true.
     return true;