[Uno-d] Add strings for extensions requesting Chrome Sign in

This CL adds strings that will be used in a dialog that is shown in the
following conditions:
- The extension requests an auth token through Chrome.Identity API
- The user is signed in to the Web only. In Dice profiles, this is only
  possible if explicit browser sign in feature is enabled.

This dialog will inform the user that the extension wants them to sign
in to Chrome to be able to use their account.

Bug: b/321900930
Change-Id: I78ed09975b8ffa84e4a13477bf0cdc7487c3c9e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5613294


Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Monica Basta <msalama@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1312689}