(core) Move user profile to new page and begin MFA work

Summary:
The user profile dialog is now a separate page, in preparation
for upcoming work to enable MFA. This commit also contains
some MFA changes, but the UI is currently disabled and the
implementation is limited to software tokens (TOTP) only.

Test Plan:
Updated browser tests for new profile page. Tests for MFAConfig
and CognitoClient will be added in a later diff, once the UI is enabled.

Reviewers: paulfitz

Reviewed By: paulfitz

Subscribers: dsagal

Differential Revision: https://phab.getgrist.com/D3199

buildtools/webpack.config.js

@@ -7,6 +7,7 @@ module.exports = {
   entry: {
     main: "app/client/app.js",
     errorPages: "app/client/errorMain.js",
+    account: "app/client/accountMain.js",
   },
   output: {
     filename: "[name].bundle.js",