[Notif redesign] Update smart replies/actions

This updates the corner radius and size of smart replies and smart actions to make them pills instead of rounded rectangles.

Note that notification_2025_smart_reply_button.xml and notification_2025_smart_reply_button_background.xml are forks of smart_reply_button.xml and smart_reply_button_background.xml respectively.

Bug: 378660052
Test: manual + screenshot tests
Flag: android.app.notifications_redesign_templates
Change-Id: I78b30ce80ad6738a596232430b217286eb9d1cdc