testing/test_defs.bzl: prefix refs to native rules with `native.`.
testing/test_defs.bzl: prefix refs to native rules with `native.`.

Closes https://github.com/google/bazel-common/pull/29
Fixes https://github.com/google/flogger/issues/45

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=215522092

google/bazel-common