Add script to convert datastore-indexes.xml to index.yaml

The gcloud datastore cleanup-indexes command takes its input in index.yaml form instead of datastore-indexes.yaml form. This simple translation script allows us to generate one from the other.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=169260811

python/google/registry/scripts/BUILD

@@ -0,0 +1,20 @@
+package(default_visibility = ["//java/google/registry:registry_project"])
+
+licenses(["notice"])  # Apache 2.0
+
+py_binary(
+    name = "xml_to_index_yaml_translator",
+    srcs = ["xml_to_index_yaml_translator.py"],
+    deps = ["//python:python_directory_import"],
+)
+
+py_test(
+    name = "xml_to_index_yaml_translator_test",
+    size = "small",
+    srcs = ["xml_to_index_yaml_translator_test.py"],
+    data = [
+        "testdata/datastore-indexes.xml",
+        "testdata/index.yaml",
+    ],
+    deps = [":xml_to_index_yaml_translator"],
+)