[Notif redesign] Update size and position of conversation icon badge

We were previously updating the margins here in code behind the app
icons flag, but now that we have the forked templates we can do it there
directly (and it applies to both call layout and conversation layout).
These should be the same regardless of whether we're showing the small
icon or app icon.

Bug: 378660052
Test: visual test, screenshot tests to come later
Flag: android.app.notifications_redesign_templates
Flag: android.app.notifications_redesign_app_icons
Change-Id: I51d4c34c8671c996f7573f58363b85d1b3b8d5b9