chore: Update Pajamas navigation markup and styles

What does this MR do?

• Add Pajamas logo and brand name
• Rename <navbar> to <sidebar>
• Refactor HTML semantics for <nav> and child <ul>/<li> items
• Rename nav-sidebar SCSS variables and CSS classes to sidebar
• Update root sidebar element to <aside> to be complimentary to <main>
• Update sidebar toggle tap target and positioning when open
• Update snapshots

Relates to #1443 (closed)

Screenshots

Before

After