Introduce a new cpp toolchain_type, "test_runner_toolchain_type"
Introduce a new cpp toolchain_type, "test_runner_toolchain_type"

PiperOrigin-RevId: 426438138

katre/bazel,katre/bazel,ButterflyNetwork/bazel,bazelbuild/bazel,cushon/bazel,bazelbuild/bazel,katre/bazel,cushon/bazel,ButterflyNetwork/bazel,ButterflyNetwork/bazel,bazelbuild/bazel,cushon/bazel,katre/bazel,cushon/bazel,katre/bazel,ButterflyNetwork/bazel,ButterflyNetwork/bazel,bazelbuild/bazel,katre/bazel,bazelbuild/bazel,cushon/bazel,cushon/bazel,ButterflyNetwork/bazel,bazelbuild/bazel