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

Empieza leyendo el componente MissingPage y compara su API de footer con ErrorState, que ya admite customFooter. Confirma cómo se renderiza la acción toHomePageUrl existente y, después, añade una forma compatible de renderizar varias acciones personalizadas conservando el comportamiento actual. Se considera terminado cuando los consumidores pueden proporcionar acciones de inicio y de volver sin duplicar el layout de MissingPage.