Use messaging system for save state confirmation

[rschamp]

Somewhat a duplicate of #2811

Follow up for #3021 (comment)

Use the messaging components needed for showing hardware status changes in order to show the save status (in progress, completed, errored)

[kyleplo]

I think it should only show when errored, because it would be annoying if every time it autosaves, a message pops up.

[benjiwheeler]

This was basically closed by #3638 .

The only non-closed aspect is the display of errors, which is tracked in #3324 .

@kyleplo , you're right! So per #3638 , auto-saves are not using the alert system.