[distribute] Add LICENSE to python ancillary packages. (#33574)

Fix: #33557

### Testing
* Verified through `distribtests_python` that `LICENSE` file exists in
both
[.tar.gz](https://storage.googleapis.com/grpc-testing-kokoro-prod/test_result_public/prod/grpc/core/pull_request/linux/f69791e2-b7fd-4729-b55e-caca9171a170/1/20230629-092736/github/grpc/artifacts/grpcio-status-1.57.0.dev0.tar.gz)
and
[.whl](https://storage.googleapis.com/grpc-testing-kokoro-prod/test_result_public/prod/grpc/core/pull_request/linux/f69791e2-b7fd-4729-b55e-caca9171a170/1/20230629-092736/github/grpc/artifacts/grpcio_status-1.57.0.dev0-py3-none-any.whl).

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tools/run_tests/artifacts/build_artifact_python.sh

@@ -81,6 +81,21 @@ then
   export GRPC_BUILD_OVERRIDE_BORING_SSL_ASM_PLATFORM="linux-arm"
 fi
 
+ancillary_package_dir=(
+  "src/python/grpcio_admin/"
+  "src/python/grpcio_channelz/"
+  "src/python/grpcio_csds/"
+  "src/python/grpcio_health_checking/"
+  "src/python/grpcio_reflection/"
+  "src/python/grpcio_status/"
+  "src/python/grpcio_testing/"
+)
+
+# Copy license to ancillary package directories so it will be distributed.
+for directory in "${ancillary_package_dir[@]}"; do
+  cp "LICENSE" "${directory}"
+done
+
 # Build the source distribution first because MANIFEST.in cannot override
 # exclusion of built shared objects among package resources (for some
 # inexplicable reason).