Do not delete "fake" source map comments from strings (#9960)

Instead of using `convert-source-map`'s `removeComments` method before
parsing the file, we can first parse the file with `@babel/parser` and then
analyze the comments.
This is needed because it is not possible to reliabily detect comments in
JavaScript without fully parsing the file:
https://github.com/thlorenz/convert-source-map/issues/63

packages/babel-types/src/traverse/traverseFast.js

@@ -7,7 +7,7 @@ import { VISITOR_KEYS } from "../definitions";
  */
 export default function traverseFast(
   node: Object,
-  enter: (node: Node, opts?: Object) => void,
+  enter: (node: BabelNode, opts?: Object) => void,
   opts?: Object,
 ): void {
   if (!node) return;