[Settings] Refactor Wifi Calling description text

Refactor the display of description text when no wifi calling options available.
Enhancement:
1. These text need to align the style with the summary part of the wifi
calling options.
2. These text need to be scrollable in order to see full description.
3. The link within text need to be clickable.

Bug: 204844012
Test: local
Change-Id: Ie89a5b65e75cdd61fab68c6e1bf7c40bfcc68b6b