Improve logging of embed failure

There's a lot of issue about embed failure from 1P apps.
Usually, it's because the Activity is going to launch on a new Task,
which is not allowed to embed.
This Cl tries to improve the logging to make 1P developers know how
to fix the embed failure.

fixes: 234414942
Test: presubmit
Change-Id: Id0ea961997afdec2b4f7d49c56f76e9ffc2f0360