Add a package to open source

Add {java,tests}/google/registry/export/datastore to open source.
This is part of the migration to Datastore Managed Import/Export
for backup.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=221800709

javatests/google/registry/export/datastore/BUILD

@@ -0,0 +1,35 @@
+package(
+    default_testonly = 1,
+    default_visibility = ["//java/google/registry:registry_project"],
+)
+
+licenses(["notice"])  # Apache 2.0
+
+load("//java/com/google/testing/builddefs:GenTestRules.bzl", "GenTestRules")
+
+java_library(
+    name = "datastore",
+    srcs = glob(["*.java"]),
+    resources = glob(["**/testdata/*.json"]),
+    deps = [
+        "//java/google/registry/export/datastore",
+        "//javatests/google/registry/testing",
+        "//third_party/java/google_http_java_client:http",
+        "//third_party/java/google_http_java_client:javanet",
+        "//third_party/java/google_http_java_client:util",
+        "@com_google_api_client",
+        "@com_google_guava",
+        "@com_google_http_client",
+        "@com_google_http_client_jackson2",
+        "@com_google_truth",
+        "@com_google_truth_extensions_truth_java8_extension",
+        "@junit",
+        "@org_mockito_all",
+    ],
+)
+
+GenTestRules(
+    name = "GeneratedTestRules",
+    test_files = glob(["*Test.java"]),
+    deps = [":datastore"],
+)