Ability to add ActionGroup to extraModalFooterActions

[GeminiDev1]

Currently, we're able to add multiple instances of actions to ->extraModalFooterActions().

However, when there are several buttons, the footer can look crowded. For example:

Adding support for a group action (https://filamentphp.com/docs/4.x/actions/grouping-actions#customizing-the-group-trigger-style
) would be a great way to organise actions.

(Source: https://filamentphp.com/docs/4.x/images/light/actions/group/customized.jpg)

Use case
This can allow the primary action to remain visible, while secondary actions could be placed inside a group, alongside a cancel button.