Transform JSX spread children (#45693)

* Transform JSX spread children

* Target es2015 to skip helper and refine emit

Co-authored-by: Ron Buckton <ron.buckton@microsoft.com>

Co-authored-by: Ron Buckton <ron.buckton@microsoft.com>
Co-authored-by: Orta <git@orta.io>

src/compiler/transformers/jsx.ts

@@ -547,7 +547,8 @@ namespace ts {
         }
 
         function visitJsxExpression(node: JsxExpression) {
-            return visitNode(node.expression, visitor, isExpression);
+            const expression = visitNode(node.expression, visitor, isExpression);
+            return node.dotDotDotToken ? factory.createSpreadElement(expression!) : expression;
         }
     }