TabSheetVariant.LUMO_TABS_ICON_ON_TOP is not working properly

[web-padawan]

Description

Originally reported at the forum: https://vaadin.com/forum/t/tabsheet-theme-variants-seem-to-be-ignored/167106

The vaadin-tabsheet web component delegates theme attribute to the underlying vaadin-tabs which makes most of theme variants just work (e.g. small, minimal, equal-width-tabs etc).

However, the icon-on-top variant is expected to be set on individual vaadin-tab instances, which isn't handled by vaadin-tabsheet and therefore the TabSheetVariant.LUMO_TABS_ICON_ON_TOP doesn't work as expected.

UPD: actually, the same value exists in TabsVariant since the very old version https://github.com/vaadin/vaadin-tabs-flow/pull/80 and the TabSheetVariant was most probably just a copy-paste from there 🙈

Expected outcome

Expected the theme variant to work.

Minimal reproducible example

tabSheet.addThemeVariants(TabSheetVariant.LUMO_TABS_ICON_ON_TOP);

Steps to reproduce

Use the TabSheet with several tabs with icons and set the variant.

Environment

Vaadin version(s): 24.x and older

Browsers

Issue is not browser related