Merge the pending task notifications to the notification area

[kelsos]

Abstract

Follow up issue for #3334

Part of the reasoning for this change is to reduce the icon on the top bar when on mobile.
The ongoing/pending task notifications should be merged with the message/warning notifications following a similar mechanism on how mobile and desktop OSes use a unified mechanism for both one-off notifications and notifications related to ongoing tasks.

Specification

• When there are pending tasks the bell icon transforms to a spinner icon
• Ongoing task notifications will appear on the top area and will be divided from the message type notifications