Allow summarizations to be two lines of text long

Test: manual with ConversationLayout/MessagingLayout with 2025 redesign
on and off
Test: NotificationRowContentBinderImplTest
Test: NotificationContentInflaterTest
Test: ConversationNotificationProcessorTest
Flag: android.app.nm_summarization
Flag: android.app.nm_summarization_ui
Fixes: 394825842

Change-Id: Ic276328889616feac954ef170438b11be749a6c6