For #5086, wait for old Quick Open bar to close before creating a new one. Also move some global state into the QuickNavigateDialog object.
Added clarifying comments per code review
Update scroll pos/selection synchronously after ModalBar.close() starts rather than on a timeout
Clean up logic when creating a Quick Open dialog
Merge pull request #5108 from adobe/nj/issue-5086

For #5086, wait for old Quick Open bar to fully close before creating a new one.