fix nested toolbar losing suboptions

[kecnry]

Description

This pull request fixes the case where clicking a tool in the toolbar dropdown menu could lose the ability to select other suboptions. This was happening because the "has_suboptions" on the tool was originally set to False and not updated later when it then became the "primary" tool in the sub-menu. This fix is perhaps overly conservative, but ensures that the "has_suboptions" will always be kept up-to-date in advance of choosing a new tool.

This could be reproduced in specviz2d by selecting the non-synced zoom tool in either viewer.

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.
• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?

[rosteen]

LGTM.