Navigation Overlay: Add option to replace close icon

[mikachan]

What problem does this address?

In #36149, we added the option to replace the overlay menu icon with text. However, when the overlay is open, we still use an icon for closing the overlay.

What is your proposed solution?

It would be nice to also replace the close icon with text as well (probably 'close'), as part of the hasIcon toggle. Or, we could have a separate option just for the close button.