fix(Modal): Autofocus close button, if it is the only focusable element

What does this MR do?

If there is a modal that has no focusable element in the modal content AND no modal footer, it should focus the close button.

The close button is the last focusable element we try to focus, and it doesn't work correctly because it is moved to the end of the list with the help of Array.splice which doesn't return the Element, but an array of elements.

Does this MR meet the acceptance criteria?

Conformity

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Security

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