Implementing JBrowse 2 checklist

[scottcain]

• convert remaining tracks configs.
• merge existing code into stage (putting JBrowse embedded in location widget, and "demo"/beta implementation of synteny browser)
• big issue: transition GBrowse_syn (separate checklist: #183)
• update website links to GBrowse to point at JBrowse 2
• create wormbase specific user tutorial

Not exactly related to retiring GBrowse, but needs to be done eventually (ie, these are lowest priority):

• Port sequence feature widget
• Port protein "homology" widget

[scottcain]

All of the tracks have been ported but one that I found while doing other things, because it is no longer included in JBrowse 1 for reasons that are not clear to me (see https://github.com/WormBase/website/issues/7406)