feat(ui5-notification-list-item, ui5-tab): add semantic click event

[tsanislavgatev]

NotificationListItem overrode both _onclick and fireItemPress
without calling super, bypassing the ListItemBase click event added
in #13315. Both methods now call stopPropagation on the native
event and fire the semantic click CustomEvent with { item, originalEvent }.

Tab receives its own click event fired by TabContainer after a
successful tab selection, carrying { tab, originalEvent } so
consumers can distinguish programmatic from user-initiated selection.

Add a semantic click CustomEvent that fires on both mouse/tap and
keyboard (Enter/Space) activation. It replaces the propagated native
click (via stopPropagation) with a composed CustomEvent that includes
item/tab and originalEvent in its detail, enabling consumers to
distinguish component-level clicks from raw DOM events.

ListItemBase gets the event as the base implementation for all list items.
Tab fires it from TabContainer when a tab is selected.

Fixes #13328

[ui5-webcomponents-bot]

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