Refactor beam invoicing pipeline into its own package

This prepares for the spec11 beam pipeline to live parallel to the invoicing
beam pipeline, for better organization.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=204980582

java/google/registry/tools/BUILD

@@ -35,7 +35,7 @@ java_library(
     visibility = [":allowed-tools"],
     deps = [
         "//java/google/registry/backup",
-        "//java/google/registry/beam",
+        "//java/google/registry/beam/invoicing",
         "//java/google/registry/bigquery",
         "//java/google/registry/config",
         "//java/google/registry/dns",

java/google/registry/tools/DeployInvoicingPipelineCommand.java

@@ -15,10 +15,10 @@
 package google.registry.tools;
 
 import com.beust.jcommander.Parameters;
-import google.registry.beam.InvoicingPipeline;
+import google.registry.beam.invoicing.InvoicingPipeline;
 import javax.inject.Inject;
 
-/** Nomulus command that deploys the {@link google.registry.beam.InvoicingPipeline} template. */
+/** Nomulus command that deploys the {@link InvoicingPipeline} template. */
 @Parameters(commandDescription = "Deploy the invoicing pipeline to GCS.")
 public class DeployInvoicingPipelineCommand implements Command {