[Notif redesign] Update conversation info design

I previously thought I'd changed the main guts layout behind a separate
flag instead of the templates one, but since it looks like I didn't...
I guess we can just roll with the same templates flag ¯\_(ツ)_/¯

Note that notification_2025_conversation_info.xml is a fork of
notification_conversation_info.xml.

Bug: 394822197
Test: tested manually
Flag: android.app.notifications_redesign_templates
Change-Id: I96545e967aa89665ade9e3493c1329b554a1d55a