* Add policy note to pub publish command

Includes a minor re-design of how errors and warnings are presented.
Notably prints summary of warnings in bold red text when asking if
the user wants to publish the package.

The confirmation dialog also includes the package name and version as
this may have scrolled out of view if the list of files or warnings is
huge.

* Fixed tests

Co-authored-by: Michael Thomsen <mit@google.com>