What does this add?
===================
This PR adds an extra button to the poll to show the absolute number of
people who voted for each option. This button will only be added for
the single/multi-select bar chart.
Related meta topic: https://meta.discourse.org/t/absolute-numbers-in-polls/32771
Fixes a flaky test. `afterUpdate` from chart.js is not integrated with the runloop and component lifecycle, as a result we have no guarantee on when it will happen. The easiest change we can do for now is ensuring we actually have the DOM we expect to have, and if not, we exit early.
Co-authored-by: Joffrey JAFFEUX <j.jaffeux@gmail.com>
Co-authored-by: merefield <merefield@gmail.com>
The "migration to Glimmer" has been broken out here from #27155 to make the review process less onerous and reduce change risk:
* DEV: migrates most of the widget code to Glimmer in prep for IRV additions
* NB This already incorporates significant amounts of review and feedback from the prior PR.
* NB because there was significant additional feedback relating to older Poll code that I've improved with feedback, there are some additional changes here that are general improvements to the plugin and not specific to IRV nor Glimmer!
* There should be no trace of IRV code here.
Once this is finalised and merged we can continue to progress with #27155.
