[Notif redesign] Circular icons for Call Notifications

Note that:
- notification_2025_template_collapsed_call is forked from notification_template_material_call.
- notification_2025_template_expanded_call is forked from notification_template_material_big_call.

Bug: 378660052
Test: visual test, screenshot tests to come later
Flag: android.app.notifications_redesign_templates
Change-Id: I13f7ef44077bd0bc24eabbb983c9920c70cb6861