Fire hook_quicktabs_instance_alter() in AJAX controller

J Prequested to merge
issue/quicktabs-3606674:3606674-hookquicktabsinstancealter-not-invoked into 4.0.x

QuickTabsInstance::getRenderArray() calls the alter before rendering, but QuickTabsController::ajaxContent() loads the entity and renders directly without it. Modules that set view arguments or modify tab configuration via the alter have their changes ignored on AJAX-loaded tabs.

Closes #3606674

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