Implement 10 min backoff for failed async deletes

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=117945626

java/com/google/domain/registry/config/RegistryConfig.java

@@ -256,4 +256,12 @@ public interface RegistryConfig {
    * committed, and could potentially miss the reference.
    */
   public Duration getAsyncDeleteFlowMapreduceDelay();
+
+  /**
+   * Returns the amount of time to back off following an async delete flow task failure.
+   *
+   * This should be ~orders of magnitude larger than the rate on the queue, in order to prevent
+   * the logs from filling up with unnecessarily failures.
+   */
+  public Duration getAsyncDeleteFlowFailureBackoff();
 }