Onion authentication semantic and accessibility problems

The authentication popup:

• When the popup shows it is read as a notification on screen readers. However, the notification begins with the onion address " is requesting that you authenticate", so the notification is a bunch of text noise before the relevant information is reached. Shortened in !775 (merged). There's not much we can do about onion sites unreadable names, but we could front the message with something more readable, like "An onion site is requesting that you authenticate. Learn more. Onion address: ".
• The invalid key warning (#tor-clientauth-warning) lacks semantics that show it as a warning and connected to the input, like aria-errormessage. The input is not marked as invalid. Fixed in #43263 (closed).

The onion net error page (e.g. when cancelling authentication):

• The diagram at the top of the page (#onionErrorDiagramContainer) lacks an equivalent description for screen readers. Currently you just get the text nodes with no context. Removed in #41622 (closed)
• The rest of the page is lacking some semantic structure, but it comes from mozilla.

The "Onion Service Keys" dialog in preferences:

• #onionservices-savedkeys-errorMessage could use something like aria-live to notify the user of errors. Fixed in #43263 (closed).
• The #onionservices-savedkeys-tree xul:table is lacking some accessibility features that a role="grid" would expect. But this comes from the xul:table implementation.
• The table is very obscure to read. The onion sites and keys are just long random strings, so are very bad on screen readers, but also lack context for visual users as well because it is not easy to identify the onion site. I don't know if anything can be done about this.