Daggerize/Actionize the load snapshot servlet

This is needed to eliminate the last non-injected use of BigqueryFactory.  It gets rid of the deprecated HttpServletUtils now that we don't have lots of separate servlets, and changes the check snapshot servlet's usage of such.  It also fixes up some related minor style issues in the update snapshot action (and its injectable parameters).
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=120547998

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

@@ -51,20 +51,6 @@ public interface RegistryConfig {
    */
   public String getDomainListsBucket();
 
-  /**
-   * Returns the BigQuery dataset for storing directly imported datastore snapshots.
-   *
-   * @see com.google.domain.registry.export.LoadSnapshotServlet
-   */
-  public String getSnapshotsDataset();
-
-  /**
-   * Returns the BigQuery dataset for storing views pointing to the latest datastore snapshot.
-   *
-   * @see com.google.domain.registry.export.UpdateSnapshotViewAction
-   */
-  public String getLatestSnapshotDataset();
-
   /**
    * Number of sharded commit log buckets.
    *