Lazily initialize and cache constant JSX elements (#12967)

Co-authored-by: Justin Ridgewell <justin@ridgewell.name>

packages/babel-plugin-transform-react-constant-elements/test/fixtures/integration/issue-12303/input.mjs

@@ -0,0 +1,6 @@
+function Foo({outsetArrows, ...rest}) {
+  return useMemo(
+    () => <div outsetArrows={outsetArrows}/>,
+    [outsetArrows]
+  );
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/integration/issue-12303/options.json

@@ -0,0 +1,7 @@
+{
+  "plugins": [
+    "syntax-jsx",
+    "transform-react-constant-elements",
+    "proposal-object-rest-spread"
+  ]
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/integration/issue-12303/output.mjs

@@ -0,0 +1,9 @@
+function Foo(_ref) {
+  var _div;
+
+  let {
+    outsetArrows
+  } = _ref,
+      rest = babelHelpers.objectWithoutProperties(_ref, ["outsetArrows"]);
+  return useMemo(() => _div || (_div = <div outsetArrows={outsetArrows} />), [outsetArrows]);
+}