[TIMOB-10327] iOS: Add support for accessing and manipulating TableViewSections from a TableView

Accessing table view sections from a table view is currently limited to the data property which resets the entire table. This makes it extremely expensive to, say, add a new section to an already existing table. It has also given rise to poorly thought out API designs such as the 'header' property of TableViewRows. We need to add methods for accessing and manipulating TableViewSections in a TableView akin to how we can access TableViewRows from a TableView. We also need to document and deprecate the previously undocumented 'header' property.