ci: use cache_test_results=auto for non-ci/daily bazel builds (#6879)
ci: use cache_test_results=auto for non-ci/daily bazel builds (#6879)

Recently we moved to `--cache_test_results=no` for CI, and then
daily bazel builds (see #6773 and #6806).  An upshot of this was
that we also moved to `--cache_test_results=yes` for the other
bazel builds.

However, `--cache_test_results=yes` is not the same as defaulting
the flag.  In particular, `yes` indicates that test failures
should be cached, which is undesirable when those tests are flaky.

So restore those other bazel builds to the default caching mode
of `--cache_test_results=auto`, which always reruns failed tests
(and also reruns under `--runs_per_test`).
googleapis/google-cloud-cpp,googleapis/google-cloud-cpp,googleapis/google-cloud-cpp,googleapis/google-cloud-cpp