Convert CommonJS exports to ES6-compatible exports

We use `export default` begrudgingly here. Ideally we'd use just `export`, though this entire SDK expects things to be exported as a default. Instead of breaking everything, we'll sacrifice our export pattern for a smaller diff - a later commit can always do the default export -> regular export conversion.

test/end-to-end-tests/src/rest/session.js

@@ -19,7 +19,7 @@ const Logger = require('../logger');
 const RestRoom = require('./room');
 const {approveConsent} = require('./consent');
 
-module.exports = class RestSession {
+export default class RestSession {
     constructor(credentials) {
         this.log = new Logger(credentials.userId);
         this._credentials = credentials;