[webview_flutter_wkwebview] Return an NSNumber that represents a bool (flutter#5968)

Author: bparrishMines

packages/webview_flutter/webview_flutter_wkwebview/example/ios/RunnerTests/FWFWebsiteDataStoreHostApiTests.m

@@ -70,6 +70,8 @@ - (void)testRemoveDataOfTypes {
                                         blockError = error;
                                       }];
   XCTAssertEqualObjects(returnValue, @YES);
+  // Asserts whether the NSNumber will be deserialized by the standard codec as a boolean.
+  XCTAssertEqual(CFGetTypeID((__bridge CFTypeRef)(returnValue)), CFBooleanGetTypeID());
   XCTAssertNil(blockError);
 }
 @end

packages/webview_flutter/webview_flutter_wkwebview/ios/Classes/FWFWebsiteDataStoreHostApi.m

@@ -60,7 +60,7 @@ - (void)createDefaultDataStoreWithIdentifier:(nonnull NSNumber *)identifier
                       modifiedSince:[NSDate dateWithTimeIntervalSince1970:
                                                 modificationTimeInSecondsSinceEpoch.doubleValue]
                   completionHandler:^{
-                    completion(@(records.count > 0), nil);
+                    completion([NSNumber numberWithBool:(records.count > 0)], nil);
                   }];
             }];
 }