Refactor StringGenerator bindings

Make every dependency request explicit on what encoding is used. Also get rid of InjectRule in XjcToDomainResourceConverterTest.

Random number generator providers are separated to secure and insecure ones. The insecure ones must be explicitly requested (usually for use cases where security is not of concern, for better speed).

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=217921422

java/google/registry/tools/CreateAnchorTenantCommand.java

@@ -25,6 +25,7 @@ import com.beust.jcommander.Parameter;
 import com.beust.jcommander.Parameters;
 import com.google.common.net.InternetDomainName;
 import com.google.template.soy.data.SoyMapData;
+import google.registry.config.RegistryConfig.Config;
 import google.registry.tools.soy.CreateAnchorTenantSoyInfo;
 import google.registry.util.StringGenerator;
 import javax.inject.Inject;
@@ -72,6 +73,7 @@ final class CreateAnchorTenantCommand extends MutatingEppToolCommand {
   private boolean fee;
 
   @Inject
+  @Config("base64StringGenerator")
   StringGenerator passwordGenerator;
 
   @Override