Fix data package read/load failures using the refactored package components #2806
Description
MetacatUI's current package/resource map loading behaviour sometimes leads to intermittent missing files and package displays that do not re-render correctly until the page is refreshed. This PR will fix data package loading and rendering behaviour in the data package view using the new lower-level classes introduced in #2804, including:
- Improved resource map resolution when the resource map is missing from the index or there are multiple resource maps for the given PID.
- Fixes for re-render issues in the data package display so package contents update more reliably when models finish loading
- More reliable process to fetch information about package members (via solr or sysMeta)
- Unit tests for the new package/resource-map load behaviours