Part 1 of migrating passwordmgr.properties to fluent: Converting the strings from LoginManagerPrompter
1. The following strings [saveLoginMsg2, saveLoginMsgNoUser2, saveLoginButtonDeny.label, saveLoginButtonDeny.accesskey, updateLoginMsg3, updateLoginMsgNoUser3, updateLoginButtonDelete.label, updateLoginButtonDelete.accesskey] are not migrated as the messages are changed. They get replaced by [save-password-message, save-password-button-deny, update-password-messsage, update-password-button-delete]
2. The remaining string from LoginManagerPrompter are migrated by the python script.
Differential Revision: https://phabricator.services.mozilla.com/D195931