chore: Integrate new gapic-generator-java and rules_gapic (#768)

* chore: Integrate new gapic-generator-java and rules_gapic

PiperOrigin-RevId: 454027580

Source-Link: googleapis/googleapis@1b22277

Source-Link: https://github.com/googleapis/googleapis-gen/commit/e04cea20d0d12eb5c3bdb360a9e72b654edcb638
Copy-Tag: eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiZTA0Y2VhMjBkMGQxMmViNWMzYmRiMzYwYTllNzJiNjU0ZWRjYjYzOCJ9

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: gcf-owl-bot[bot]

google-cloud-datastore/src/main/java/com/google/cloud/datastore/admin/v1/DatastoreAdminClient.java

@@ -888,7 +888,7 @@ public final ListIndexesPagedResponse listIndexes(ListIndexesRequest request) {
    *           .build();
    *   while (true) {
    *     ListIndexesResponse response = datastoreAdminClient.listIndexesCallable().call(request);
-   *     for (Index element : response.getResponsesList()) {
+   *     for (Index element : response.getIndexesList()) {
    *       // doThingsWith(element);
    *     }
    *     String nextPageToken = response.getNextPageToken();