Improve hiddenapi exclude.sh script

Changes:
* Adds a missing package for libcore.
* Splits the android.icu package out into a new I18N team.
* Corrects and splits the conscrypt package out into a new CONSCRYPT
  team.
* Fixes some issues that arose due to multiple teams.
* Reports multiple issues instead of stopping at the first one.
* Only reports issues with additions/changes not removals.

Bug: 177892522
Test: tools/hiddenapi/exclude.sh <SHA>
      Ran it on a number of different commits with different
      changes.
Change-Id: I44740a28a56a26ee7fba3ed691d9da34f4effa8a