Ensure disabling via AJAX doesn't result in errors of the link is clicked multiple times while processing is still happening.

[pbiron]

This addresses the 2nd part of #94.

It also fixes incorrect aria-labels in the AJAX results and harmonizes wp_autoupdates_enable_auto_updates() and wp_autoupdates_disable_auto_updates() so their code structure more closely aligns with one another.

[azaozz]

Right, the patch fixes the multiple click/multiple returns bug but the code there generally can probably be better. Will add inline comments.

[azaozz]

Another UI thing that may need considering/fixing:

Seems a lot of repetition, also some inconsistency?

• The table column shows the auto-updating setting status, but it should show it for both enabled and disabled.
• Is all the repetition really needed?
• Is the additional repetition in the link's aria-label needed? Seems screen readers will get something like: "Automatic updates, Auto-updates enabled, Disable auto-updates, Disable automatic updates for Classic Editor".

Edit: ugh, this is in the wrong place, sorry. Moving to https://github.com/WordPress/wp-autoupdates/issues/94.