Save number of years in DomainApplication

Right now, DomainApplicationCreateFlow checks to make sure that the registration period is in years, but doesn't store it in the DomainApplication explicitly. Instead, when DomainAllocateFlow runs later, it goes back to the XML in the HistoryEntry to get the number of years. Corey suggests that it would be cleaner to store the number of years in the DomainApplication. This is stage one of a data migration; we store the value, but don't actually read it anywhere except in tests. If we have any outstanding domain applications, we will then need to write a scrap tool to populate the years field, after which we can start relying on the field.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=137317739

java/google/registry/flows/domain/DomainApplicationCreateFlow.java

@@ -218,6 +218,7 @@ public final class DomainApplicationCreateFlow extends LoggedInFlow implements T
         .setLaunchNotice(launchCreate == null ? null : launchCreate.getNotice())
         .setIdnTableName(idnTableName)
         .setPhase(launchCreate.getPhase())
+        .setYears(command.getPeriod().getValue())
         .setApplicationStatus(ApplicationStatus.VALIDATED)
         .addStatusValue(StatusValue.PENDING_CREATE)
         .setDsData(secDnsCreate == null ? null : secDnsCreate.getDsData())