Add hooks in API action=createaccount for Captcha

New hooks:
* AddNewAccountApiForm
* AddNewAccountApiResult

These hooks are used in ConfirmEdit here: Id628def

Sample API client: https://github.com/brion/api-createaccount

Bug: 46072

Change-Id: If5b7dab80ac85dbfa0f7a54a445356783df5e914
Merge "Add hooks in API action=createaccount for Captcha"