feat(Listbox): Add startOpened prop

mentioned in commit be2b759f

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!215 (merged)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!218 (closed)

mentioned in merge request gitlab!134006 (merged)

mentioned in merge request gitlab-docs!4315 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3573 (merged)

mentioned in merge request status-page!881 (merged)

mentioned in merge request status-page!883 (merged)