[TabBar] Vertically center text tab labels (#2023)
[TabBar] Vertically center text tab labels (#2023)

Text-only tabs should vertically center their labels.

Closes #1321

randallli/material-components-ios,randallli/material-components-ios,samnm/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,samnm/material-components-ios,samnm/material-components-ios,brianjmoore/material-components-ios,randallli/material-components-ios,brianjmoore/material-components-ios,brianjmoore/material-components-ios,material-components/material-components-ios,samnm/material-components-ios,sigito/material-components-ios,sigito/material-components-ios,willlarche/material-components-ios,willlarche/material-components-ios,willlarche/material-components-ios,samnm/material-components-ios,brianjmoore/material-components-ios,sigito/material-components-ios,willlarche/material-components-ios,randallli/material-components-ios,randallli/material-components-ios,sigito/material-components-ios,brianjmoore/material-components-ios,material-components/material-components-ios,sigito/material-components-ios,material-components/material-components-ios,randallli/material-components-ios,willlarche/material-components-ios