Platform: Account Branch Name in "Select Account" List.

Add branch name and maybe mailing address to the list of accounts when asked to select an account on /auth/account/choose-existing page.

Will need to make a separate call to auth or update the core layer to get this extra info.

Needs: `$authApi('/users/orgs')`

Start at the /auth/account/choose-existing page and trace the account list request using $authApi('/users/orgs'). Determine whether the needed branch name and mailing address are available there or require an auth/core change. Done means the account choices display the branch name, with the mailing address included if supported, and the account-selection flow still works.

Written by the indexing model from the issue text.