[A11y] Improve copy button accessibility

[loic-sharma]

Background

The Bootstrap 3 popover does not work well with Windows Narrator. Previously, we worked around this by "flashing" the button's pressed state (we set the button's aria-pressed to true, wait 1.5 seconds, then set it back to false). Now, we work around this by giving the popover a role of status, which causes Windows Narrator to read the content (Narrator refuses to announce labels with the tooltip role).

Addresses: #8607
Addresses: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1061326

Testing

This change passes Accessibility Insights FastPass:

Windows Narrator

Here is what Windows Narrator announces when you tab to the copy button:

• Before: Table, Copy the package manager command, button, off
• After: Table, Copy the package manager command, button

Here is what Windows Narrator announces when you press the copy button:

• Before: Copy the package command, button, Copy the package command, button, on
• After: Copied, end of line

NVDA

Here is what NVDA announces when you tab to the copy button:

• Before: Copy the package manager command, toggle, button, not pressed
• After: Copy the package manager command, button

Here is what NVDA announces when you press the copy button:

• Before: Copied, copied, pressed, not pressed
• After: Copied, copied