Gtest support in Arcadia

Gtest wrapper that reports results exactly how Arcadia CI wants it.

How to use:

• use GTEST in your ya.make;
• include gtest.h from this library. Don't include <gtest/gtest.h> and <gmock/gmock.h> directly because then you'll not get our extensions, including pretty printers for util types;
• write tests and enjoy.