* View a unit page, which has its own URL
* Components appear within a unit as full previews. Their top bar shows type icon and title on the left, and draft status (if any), tag count, overflow menu, and drag handle on the right.
* Components have an overflow menu within a unit
* Components can be selected within a unit
* When components are selected, the standard component sidebar appears. The preview tab is hidden, since component previews are visible in the main content area.
* Components within a unit full-page view have hover and selected states
* Unit sidebar preview.
* Frontend implementation Drag-n-drop components to reorder them in unit.
Fixes some a11y and performance issues for Library Authors
**Accessibility**
* When navigating between the various Library Authoring pages, the search keyword box should not be auto-focused, so focus will follow the user's click/tab events and keep that continuity.
The course content search modal behavior is unchanged -- loading this modal auto-focuses the search input box as one would expect.
**Performance**
* Navigating between the various Library Authoring pages was causing a full re-mount of the `<LibraryLayout/>` component
* React query's `staleTime` option is used to control how long data is considered fresh in both queries and routes. By default, the `staleTime` for queries is set to 0 milliseconds, meaning that the data will always be considered stale and will be refetched whenever the query is mounted.
Adds new routes and URL parameters to use when viewing and performing searches on library components. These changes allow these pages to be bookmarked or shared by copy/pasting the browser's current URL.
No changes were made to the UI.
Use cases covered:
* As an author working with content libraries, I want to easily share any component in a library with other people on my team, by copying the URL from my browser and sending it to them.
* As an author working with content libraries, I want to easily share any search results with other people on my team, by copying the URL from my browser and sending it to them.
* As an author working with content libraries, I want to bookmark a search in my browser and return to it at any time, with the same filters and keywords applied.
* As an author of a content library with public read access, I want to easily share any component in a library with any authors on the same Open edX instance, by copying the URL from my browser and sending it to them.
* As an author of a content library, I want to easily share a library's "Manage Team" page with other people on my team by copying the URL from my browser and sending it to them.
* As an author working with content libraries, I want to easily share any selected sidebar tab with other people on my team, by copying the URL from my browser and sending it to them.
* feat: enable the problem editor for library components
* fix: don't try to load "advanced settings" when editing problem in library
* fix: don't fetch images when editing problem in library
* docs: add a note about plans for the editor modal
* fix: choosing a problem type then cancelling resulted in an error
* chore: remove unused mockApi, clean up problematic 'module' self import
* test: update workflow test to test problem editor
* feat: show capa content summary on cards in library search results
* docs: fix comment typos found in code review
* refactor: add 'key-utils' to consolidate opaque key logic
