React/Styles: Refactor Navigation & Local Navigation

[justintemps]

⚠️ This cannot be released to production until #823 has also been finished and merged

The Navigation component is a big unwieldy mess that renders both the primary Navigation (as seen on ilo.org) and the Local Navigation (as seen on sub-sites like ILO Live).

The scope of this ticket is to disentangle those into two completely separate components:

• Navigation
• Local Navigation

At the same time, the LocalNavigation component has undergone design changes that are detailed in Figma.

Main changes:

• Rename component: 'Local nav' becomes 'Subsite Nav'
• Subsite Nav component has two variants: Complex and Simple. See all changes in the designs.
• Subsite Nav must always show ILO logo + subsite name.
• Tablet breakpoints were added.
• Sub-site nav now supports search. Search icon can either link to a search page or open the search sub-nav.
• Sub-site nav now supports sub-nav ('More' button). 'More' button opens sub-nav component.
• Mobile sub-nav has a new link which didn't exist before ('Go to ILO website').

Original tickets for reference: #1047 ; #1228

We'll prioritize development of the Simple version which is the one to be used in ILO Live.