Isolated exec tests (#11531)

* Run exec tests in fresh contexts

* Reevaluate modules in every context

* Cache module code when running tests

* Eliminate weakmap accesses as much as possible

* Remove old multiline usage

* Using bundled polyfill to significantly increase performance

The individual requires for each file were the part that was sooooo slow.

* Drop LRU cache size

* Fixes

* Fix test

Co-authored-by: Huáng Jùnliàng <jlhwung@gmail.com>

packages/babel-plugin-transform-spread/test/fixtures/spread/array-symbol-unsupported/exec.js

@@ -1,10 +1,6 @@
 var a = (() => [2, 3])();
 
 // Simulate old environment
-let _Symbol = Symbol;
-Symbol = void 0;
-try {
-  expect([1, ...a]).toEqual([1, 2, 3]);
-} finally {
-  Symbol = _Symbol;
-}
+global.Symbol = void 0;
+
+expect([1, ...a]).toEqual([1, 2, 3]);

packages/babel-plugin-transform-spread/test/fixtures/spread/non-iterable/exec.js

@@ -5,6 +5,6 @@ expect(() => [...undefined]).toThrow(/spread non-iterable/);
 expect(() => [...o]).toThrow(/spread non-iterable/);
 
 // Simulate old browser
-Symbol = void 0;
+global.Symbol = void 0;
 
 expect(() => [...o]).toThrow(/spread non-iterable/);