Checker: Rename assertions to statements

Credits: this patch was originally written by David Brazdil
(dbrazdil@google.com) and remained untouched.

Author:    Fabio Rinaldi
Committer: Artem Serov

Bug: 147876827
Test: art/tools/checker/run_unit_tests.py
Change-Id: Ib166fe4160508fc8c9ff0dbf0590ecd89b94c247
8 files changed