LPS-49327 Get time zone value from bean; if not found, get from portal settings

Hello @natecavanaugh.
While trying to implement a story in the calendar and found that <aui:input> could not use the value from the model field if its time is timeZoneId. It sounded both unexpected and impractical so I proposed [a ticket](https://issues.liferay.com/browse/LPS-49327). Here is a pull request with a proposed solution.