Add EXPECT_STREQ and ASSERT_STREQ macros to IntegrationTest/test.h using
cpp::string_view. Note that, unlike the unit test macro (but like
googletest), this version treats NULL as distinct from "". The
inconsistency is unfortunate, but I think it's important as the code is
used for testing functions like getenv(), where "" and NULL have very
different meanings.
We should probably follow this up with a change to make the unit test
macro behave the same way.
Update integration tests to use the new macros instead of handrolled
string equality functions (my_streq), strcmp, inline_strcmp, or
string_view wrappers.