CLDR-17658 Improve Dashboard performance and UI; work in progress

[btangmu]

-For now, change only the front end

-Combine notifications in certain categories so that there is not more than one per page

-For now, apply this to both Missing and Abstained categories; easy to change which categories are affected

-Try to fix delayed visibility of checkbox click; alternatives and debugging for catCheckmarkChanged

-Remove delay from a-spin pending solution to delayed visibility of checkbox click

-Add Vue version to the About page; bugs may depend on Vue version

CLDR-17658

• [ ] This PR completes the ticket.

ALLOW_MANY_COMMITS=true

[macchiati]

I pushed to staging to try it out. Good progress!

• MUCH more responsive when there are many abstained!
• Logged in as a TC, I still don't see Abstained label (minor, but we wanted to fix this now that TCs wouldn't be overwhelmed by Abstained items)
• When I voted on an item, the Abstained dashboard row disappeared. But there were still Abstaineds on that page, and the Dashboard row it wasn't replaced by another Abstained dashboard row on that page, even after closing and opening the dashboard. [I'm guessing that that is a WIP. We were thinking of having a Dashboard row with just Section-Page that always goes to the first Abstained on the Page, but it is simpler to always just replace the one voted on by the next in the page (keeping the details of header and code, that would be fine.]

[btangmu]

As discussed in infra meeting, I'm making this ready for review in spite of remaining problems. The dashboard doesn't update properly after voting. A work-around may be to refresh the dashboard frequently using the "↻" button.

[macchiati]

Just got back to this; merging since Steven reviewed