Move rendering logic for inline suggestions to ExtServices.

Added a render service in ExtServices to connect to the renderer in
androidx.autofill for inline suggestion slices.

Cleaned up old UI rendering code that lived in system_server.

Bug: 146453086
Test: atest ExtServicesUnitTests
Change-Id: I25a7ea438afe524683671c850625ae80dacccfaa
15 files changed