[Minimal HUN] Clean up circle cropping from NotificationRowIconView

NotificationRowIconView represents small notification and it is not meant to be used to render conversation avatar.
When we enable app icon refactor, minimal hun users will not see the conversation avatar for 1-1 conversations instead application icon.
This CL cleans up circulation logic from NotificationRowIconView.java and Notification.java. Circle cropping is done in xml with background and clipToOutline

Bug: 270709257
Bug: 379253524
Test: Post a conversation notification with  Notify2 and see that icon is circular in minimal HUN.
Flag: EXEMPT trivial change
Change-Id: I1453e4c01a08eefbb8c59a9f15baa1532513643e