Add "bazelified" non-bazel tests. See tools/bazelify_tests/README.md for
the core idea.
- add a bunch of test targets that run under docker and execute tests
that correspond to `run_tests.py -l LANG ...`
- many more tests can be added in the future
- to enable running some of the C/C++ portability tests easily, added
support for `--cmake_extra_configure_args` in run_tests.py (the change
is fairly small).
Example passing build that shows how test results are structured:
https://source.cloud.google.com/results/invocations/21295351-a3e3-4be1-b6e9-aaf52195a044/targets
Jan Tattermusch