Do not quote JSX attribute keys for IdentifierName (#8045)

Given the following

```js
a = <F new/>
```

We used to generate:

```js
a = React.createElement(F, {"new": true})
```

but now we generate

```js
a = React.createElement(F, {new: true})
```

If you need to quote these (ie for ES3 you can use
transform-property-literals)

packages/babel-helper-builder-react-jsx/src/index.js

@@ -89,14 +89,14 @@ You can turn on the 'throwIfNamespace' flag to bypass this warning.`,
       }
     }
 
-    if (t.isValidIdentifier(node.name.name)) {
+    if (t.isJSXNamespacedName(node.name)) {
+      node.name = t.stringLiteral(
+        node.name.namespace.name + ":" + node.name.name.name,
+      );
+    } else if (esutils.keyword.isIdentifierNameES6(node.name.name)) {
       node.name.type = "Identifier";
     } else {
-      node.name = t.stringLiteral(
-        t.isJSXNamespacedName(node.name)
-          ? node.name.namespace.name + ":" + node.name.name.name
-          : node.name.name,
-      );
+      node.name = t.stringLiteral(node.name.name);
     }
 
     return t.inherits(t.objectProperty(node.name, value), node);

packages/babel-plugin-transform-react-inline-elements/test/fixtures/regressions/6276/output.js

@@ -1,3 +1,3 @@
 var test = babelHelpers.jsx(T, {
-  "default": " some string "
+  default: " some string "
 });

packages/babel-plugin-transform-react-jsx/test/fixtures/react/should-add-quotes-es3/input.js

@@ -0,0 +1 @@
+var es3 = <F aaa new const var default foo-bar/>;

packages/babel-plugin-transform-react-jsx/test/fixtures/react/should-add-quotes-es3/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["transform-react-jsx", "transform-property-literals"]
+}

packages/babel-plugin-transform-react-jsx/test/fixtures/react/should-add-quotes-es3/output.js

@@ -0,0 +1,8 @@
+var es3 = React.createElement(F, {
+  aaa: true,
+  "new": true,
+  "const": true,
+  "var": true,
+  "default": true,
+  "foo-bar": true
+});

packages/babel-plugin-transform-react-jsx/test/fixtures/react/should-not-add-quotes-to-identifier-names/input.js

@@ -0,0 +1 @@
+var e = <F aaa new const var default foo-bar/>;

packages/babel-plugin-transform-react-jsx/test/fixtures/react/should-not-add-quotes-to-identifier-names/output.js

@@ -0,0 +1,8 @@
+var e = React.createElement(F, {
+  aaa: true,
+  new: true,
+  const: true,
+  var: true,
+  default: true,
+  "foo-bar": true
+});