[common] Status matchers in OSS build do not give nice errors

"16-byte object" is not a very helpful debug string -- we should figure out how to make this format itself nicely. This was matching with a C string literal via the `StatusIs()` matcher.

```
[ RUN ] ParserTest.UnterminatedEscapedUnicodeChar
xls/dslx/frontend/parser_test.cc:1858: Failure
Value of: parser.ParseModule()
Expected: has a status code that is equal to 3, and has an error message that is equal to "blah"
Actual: 16-byte object <41-FD A9-35 3D-56 00-00 00-9B 3D-35 3D-56 00-00>, whose error message is wrong
```