Test: new notifications UX

[bpasero]

Refs: #42962

• macOS @gushuro
• Linux: @Tyriar
• Windows: @dbaeumer

Complexity: 5++

Intro
The notifications system has been rewritten from scratch and the old code removed. The new system consists of three parts:

• a notification toast will fly in bottom right as soon as a notification happens and hide automatically after a certain time unless it has actions (buttons). at most 3 toasts will show at the same time and old ones hide when there are more
• the status bar will show a little bell icon and counter for each new notification that resets once you open the notification center
• the notification center is a stable list of all notifications until a notification is deleted pressing the X button. it can be opened by pressing the bell icon
• a notification consists of severity, message, primary/secondary actions, close button and source. if a message does not carry actions and its text overflows, we offer a expand action to see the full text.

Trigger Notifications
Use the following strategies to trigger notifications:

• run a small extension that makes use of the showXYMessage API and optionally add buttons to the message
• notifications without buttons and long message will show collapsed by default with a button to expand them
• notification messages support markdown links in the format: [title](url)
• trigger notifications from within VSCode (for example: check for updates when there is none, open a HTML file and follow a link that points to a file that does not exist, etc.)

Verification

Status Bar

• the counter is not getting out of sync and the behaviour makes sense to you

Toasts

• toasts are animated when appearing and they show up to max 3. toasts at the same time
• the toasts do not overflow the workbench when you resize the workbench window to become small
• toasts are expanded by default when carrying actions
• the message is always visible when the notification is expanded
• if the message includes link, you can click to open
• toasts are keyboard accessible
• screen reader support: a message is read when the toast appears and the toast itself is screen reader supported when focus moves in
• verify the various notification toast commands: notifications.hideToasts, notifications.focusToasts, notifications.focusNextToast, notifications.focusPreviousToast, notifications.focusFirstToast, notifications.focusLastToast
• a notification with the same properties as one that is already showing will cause the old one to disappear and the new one to show on top

Center

• the center shows the same contents as the notification toast in a stable list
• the center does not overflow the workbench when you resize the workbench window to become small
• when you delete a toast, it will no longer show up
• when you trigger a notification while the center is opened, you will not see a toast and and the notification simply appears to the top of the list
• a notification with the same properties as one that is already showing will cause the old one to disappear and the new one to show on top
• you see a scrollbar when the maximum size of the notification center is reached
• verify the various notification center commands: notifications.showList, notifications.hideList, notifications.toggleList, notifications.clearAll
• verify the various notification commands: notification.collapse, notification.expand, notification.toggle, notification.clear
• verify keyboard accessibility
• verify screen reader announcement