Fix className attributes rendering for navigation/navigation link block

[costasovo]

Description

This PR addresses an issue described in #19858
Both blocks support setting additional class in block settings, but the className is not applied as it should be.

I've added rendering of attributes.className for navigation block in editor environment and I've added rendering of those attributes for navigation link in both editor and front end.

How has this been tested?

Manually. I added classes: navi-class, first-level-class, second-level-class in navigation and navigation link blocks. See the results in screenshots.

Rendering in the editor

Rendering in page

Types of changes

This PR contains only additions to rendered outputs.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR. .

[earnjam]

The underlying issue for this PR was resolved in #20076, so I'm going to close this one out.