Improve the toast notifications

[going-confetti]

There's currently a few problems with our toast notifications:

• Multiple can be shown at the same time, making it harder to focus on individual problems/status updates
• There's no clear hierarchy/order of toasts

Some ideas for improvement that were discussed before:

• Limit the number of toasts shown at the same time to ~3
• Add some visual hierarchy/order by making them stack on top of one another or slightly changing the opacity of older toasts
• Make sure the user is able to read and comprehend a toast message before the toast disappears

Collaborate with Design to refine the requirements for this enhancement.