Add validation to ROID suffixes

I could've sworn we were already doing this, but apparently not? Anyway,
ROID suffixes have a number of requirements on them that weren't being
enforced, so this enforces them. All existing production data is compliant
with these requirements; the only existing bad data we have is in alpha and
sandbox.

ROID suffixes are now required to match the regex ^[A-Z0-9_]{1,8}$

See also https://tools.ietf.org/html/rfc5730

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=173400001

javatests/google/registry/testing/DatastoreHelper.java

@@ -418,10 +418,11 @@ public class DatastoreHelper {
   }
 
   public static void createTld(String tld, ImmutableSortedMap<DateTime, TldState> tldStates) {
-    createTld(
-        tld,
-        Ascii.toUpperCase(tld.replaceFirst(ACE_PREFIX_REGEX, "").replace('.', '_')),
-        tldStates);
+    // Coerce the TLD string into a valid ROID suffix.
+    String roidSuffix =
+        Ascii.toUpperCase(tld.replaceFirst(ACE_PREFIX_REGEX, "").replace('.', '_'))
+            .replace('-', '_');
+    createTld(tld, roidSuffix.length() > 8 ? roidSuffix.substring(0, 8) : roidSuffix, tldStates);
   }
 
   public static void createTld(