data-menu: enforce layer order

[kecnry]

Description

This pull request implements a sort_by option on the LayerSelect component, which defaults to the previous behavior of icon (order layer was added), but also supports zorder (shows layers on TOP first). The zorder ordering is then used for the legend, data-menu, and plot options tabs.

Note that for plot options, it is possible to subscribe to layers from multiple viewers, and they may have different zorder. In this case, the zorders are parsed and sorted based on the first viewer they are found in according to the selected viewers.

Screen.Recording.2024-11-13.at.12.52.12.PM.mov

Change log entry

• Is a change log needed? If yes, is it added to CHANGES.rst? If you want to avoid merge conflicts,
  list the proposed change log here for review and add to CHANGES.rst before merge. If no, maintainer
  should add a no-changelog-entry-needed label.

Checklist for package maintainer(s)

This checklist is meant to remind the package maintainer(s) who will review this pull request of some common things to look for. This list is not exhaustive.

• Are two approvals required? Branch protection rule does not check for the second approval. If a second approval is not necessary, please apply the trivial label.
• Do the proposed changes actually accomplish desired goals? Also manually run the affected example notebooks, if necessary.
• Do the proposed changes follow the STScI Style Guides?
• Are tests added/updated as required? If so, do they follow the STScI Style Guides?
• Are docs added/updated as required? If so, do they follow the STScI Style Guides?
• Did the CI pass? If not, are the failures related?
• Is a milestone set? Set this to bugfix milestone if this is a bug fix and needs to be released ASAP; otherwise, set this to the next major release milestone. Bugfix milestone also needs an accompanying backport label.
• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?