Widget fix

[qqmyers]

What this PR does / why we need it: This PR fixes an issue and adds several improvements:

• It addresses an issue with the original script where, as far as we can tell, it could be delayed in running until the page had additional loaded scripts and the original logic assuming that widgets.js was the last script on the page was faulty. The script now waits for the page to load and will either find the script by id (new) or will scan all scripts to find the one with widgets.js in the source (legacy support).
• It updates outdated document.write calls with ones that append the iframe/text/scripts below the original script tag
• It updates jquery to 3.6.0 as used in Dataverse (although jquery is not used in this script, it pre-loads it for widgets-host.js)
• Various cleanup/reorg

Which issue(s) this PR closes:

• Closes #

Special notes for your reviewer:

Suggestions on how to test this: Follow the instructions on the collection and dataset edit/theme and widgets panes to add a widget to some other website (I had good luck just using local html files, but any web page should work) and verify that the Dataverse content shows. For Harvard Dataverse, should be tested with the current challenges to verify that it either works or shows the "Max challenge attempts exceeded. Please refresh the page to try again!" message and doesn't silently fail.

Does this PR introduce a user interface change? If mockups are available, please link/include them here:

Is there a release notes update needed for this change?:

Additional documentation: