Add automated test for "Forgot your password"

The manual test is here: Forgot your password

Existing automated coverage

• ResetPasswordIT#resetForgottenPassword: with mail configured and an email in the profile: fills the username on the reset password page, clicks Reset password, receives the email, follows its link, sets a new password and logs in with it

Missing automated coverage

• Start from the Log-in page, click "Forgot your password?" (add a LoginPage page-object method) and assert the ResetPasswordPage form is displayed

Suggested location: xwiki-platform-core/xwiki-platform-security/xwiki-platform-security-authentication/xwiki-platform-security-authentication-test/xwiki-platform-security-authentication-test-docker/src/test/it/org/xwiki/security/authentication/test/ui/ResetPasswordIT.java

Found by comparing the XWiki 18.4.4 manual test runs against the automated tests on master (a0055f10a1a).