MissingPage: support multiple action buttons

Description

MissingPage currently supports only a single link/action via the toHomePageUrl prop (rendered as a "Go to home page" link). A common 404 page pattern includes multiple actions — typically both "Go Home" and "Go Back" buttons.

Use Case

In ansible/ansible-ui, our custom PageNotFound component renders two action buttons:

• "Go to Dashboard" (navigate to home)

• "Return to previous page" (browser back)

We cannot adopt MissingPage because it only renders one action.

Proposed Solution

Add support for custom footer actions, either via:

• A customFooter or actions prop that accepts ReactNode (most flexible)

• An additionalActions array prop alongside the existing toHomePageUrl

This would align with how other component-groups components like ErrorState support customFooter.

Current Workaround

We maintain a custom PageNotFound component that duplicates MissingPage's layout but adds a second button.

Jira Issue: PF-4547

Inizia leggendo il componente MissingPage e confronta la sua API del footer con ErrorState, che supporta già customFooter. Verifica come viene renderizzata l’azione toHomePageUrl esistente, quindi aggiungi un modo supportato per renderizzare più azioni personalizzate mantenendo il comportamento attuale. Il lavoro è completo quando i consumer possono fornire sia azioni per la home sia azioni per tornare indietro senza duplicare il layout di MissingPage.