Fix matrix similarity test on arm64

Addresses precision issue by using a simpler test.
Also fixes issues with IvMatrix::preservesRightAngles, and adds unit tests.

BUG=skia:2405
R=robertphillips@google.com, egdaniel@google.com, djsollen@google.com, reed@google.com

Author: jvanverth@google.com

Review URL: https://codereview.chromium.org/520123002
3 files changed