feat: ActionGroup in HeaderAction

[pintend]

Update php type from Action to Action | ActionGroup on the prepareAction method

This allows us to pass ActionGroup objects as Actions


UseCase:

Section::make()
    ->headerActions([
        ActionGroup::make([
            SomeAction::make(),
        ]),
    ])

[People-Sea]

Please rebase onto 4.x

[danharrin]

As above, please reopen on 4.x

[pintend]

Replaced by #19431