Remove deprecated navigation styles

[bartaz]

Done

• Removes deprecated navigation styles (and sub navigation)
• Removes deprecated examples and docs
• Cleans up the navigation code from unnecessary %placeholders (that were used to share styles between deprecated and new versions)

Part of #3744

Code review

• Because of a lot of changes and code shifting in the file it may be hard to review it in a diff format. Probably it may be easier to look into how the SCSS file looks like in the end.

QA

• Open demo
• Review ALL navigation examples (light, dark, with or without dropdowns, etc), make sure they work well in all cases (big/small screen sizes, hover on items, etc)
• Review updated documentation:
  • https://vanilla-framework-3947.demos.haus/docs/patterns/navigation
  • Make sure docs don't mention any of the deprecated class names

[webteam-app]

Demo starting at https://vanilla-framework-3947.demos.haus

[sowasred2012]

Nice!