Fix structure nav for multi-sectioned IA manifests - #876

Related issue: #818

Following changes are made in this PR to improve structured navigation for Canvas ranges without mediafragment information. The IA Manifest in question has multiple canvases and are referenced in the structures property with the relevant Canvas ids. However, these ids don't have mediafragment information attached as expected by Ramp, e.g. url#t=0,2.0.
While working on this, I came across that if such ranges referencing to sections has children the collapsible UI is not operable by using left/right arrow keys to collapse/expand the sections as expected. This breaks accessibility for such structure displays. So, this PR has an additional fix to that as well.

Changes in the PR:

• formatting the id with mediafragment in the parser, so that click handlers have required information to provide desired functionality (Related Manifest: https://iiif.archive.org/iiif/3/Weirdos_demo-1978/manifest.json)
• changing the creation of sectionRef when building structured navigation to use fresh refs for each section, which fixes automatic scrolling to the last section every time the page loads or a Canvas is changed. Observe this behavior for the IA Manifest at https://ramp.avalonmediasystem.org/?iiif-content=https://iiif.archive.org/iiif/3/Weirdos_demo-1978/manifest.json.
• keeping keyboard-accessibility of such sections for collapsing/expanding sections using left/right arrow keys. Observe this behavior for a cookbook Manifest by following these steps to reproduce this behavior:
  1. Open cookbook Manifest in Ramp
  2. Use Tab key to navigate to the structure
  3. Once the focus is on the structure container (blue highlight around the structure), press ArrowDown key to move focus inside the structure
  4. Keep pressing ArrowDown until focus is on Atto Primo structure item
  5. Press ArrowLeft -> nothing happens (this should ideally collapse the section), press ArrowRight -> nothing happens (this should ideally move the focus to the first structure child under this section)