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-block-scoping/test/fixtures/general/issue-10339/exec.js

@@ -1,12 +1,12 @@
-const code = multiline([
-  "for (const {foo, ...bar} of { bar: [] }) {",
-    "() => foo;",
-    "const [qux] = bar;",
-    "try {} catch (e) {",
-      "let quux = qux;",
-    "}",
-  "}"
-]);
+const code = `
+  for (const {foo, ...bar} of { bar: [] }) {
+    () => foo;
+    const [qux] = bar;
+    try {} catch (e) {
+      let quux = qux;
+    }
+  }
+`;
 
 let programPath;
 let forOfPath;