Only bundle the release build, and don't import src in tests (#13978)

* Only bundle the release build, and don't import `src` in tests

* Use file extension to signal skipping

* Remove unnecessary config change

* Fix imports

packages/babel-parser/test/unit/util/identifier.skip-bundled.js

@@ -1,7 +1,7 @@
 import {
   isKeyword,
   keywordRelationalOperator,
-} from "../../../src/util/identifier.js";
+} from "../../../lib/util/identifier.js";
 
 describe("identifier", () => {
   describe("isKeyword", () => {

packages/babel-parser/test/unit/util/location.skip-bundled.js

@@ -1,4 +1,4 @@
-import { getLineInfo } from "../../../src/util/location.js";
+import { getLineInfo } from "../../../lib/util/location.js";
 
 describe("getLineInfo", () => {
   const input = "a\nb\nc\nd\ne\nf\ng\nh\ni";