Add "create_cdns_tld" command to nomulus

Add a command to allow us to create the managed zone for a new TLD in cloud
dns.

Note: this implementation is problematic, it's currently doing its own thing
as far as credentials and http transport, making it unusable with the []
channel and the credentials generated by login.  Unfortunately, fixing the
plumbing to make it work right is difficult, and we have an immediate need for
this functionality.

b/67367533 created to clean this up, along with related warts in the codebase.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=170906329

java/google/registry/tools/RegistryTool.java

@@ -36,6 +36,7 @@ public final class RegistryTool {
           .put("convert_idn", ConvertIdnCommand.class)
           .put("create_anchor_tenant", CreateAnchorTenantCommand.class)
           .put("create_auction_credits", CreateAuctionCreditsCommand.class)
+          .put("create_cdns_tld", CreateCdnsTld.class)
           .put("create_contact", CreateContactCommand.class)
           .put("create_credit", CreateCreditCommand.class)
           .put("create_credit_balance", CreateCreditBalanceCommand.class)