Consolidate and streamline linking in jdaviz

[stscijirahubjdat]

Issue JDAT-5009 was created on JIRA by Jesse Averbukh:

The link_new_data method in app.py is adding duplicate links with the conditionals at the start of the method and the for loop at the end. This ticket is for understanding what each links are accomplishing and then moving things around so that the fewest links are created when data is added. It also looks like link_new_data is being called multiple times when data is added, so this ticket should try to streamline that process as well.