Move two enums from FlowRunner to FlowTestCase.

They are only needed in test code.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=125126550

javatests/google/registry/testing/TestSessionMetadata.java

@@ -25,6 +25,7 @@ public class TestSessionMetadata extends SessionMetadata {
 
   private final Map<String, Object> properties = new HashMap<>();
   private boolean isValid = true;
+  private boolean isDryRun = false;
   private SessionSource sessionSource = SessionSource.NONE;
 
   @Override
@@ -57,6 +58,15 @@ public class TestSessionMetadata extends SessionMetadata {
     sessionSource = source;
   }
 
+  public void setIsDryRun(boolean isDryRun) {
+    this.isDryRun = isDryRun;
+  }
+
+  @Override
+  public boolean isDryRun() {
+    return isDryRun;
+  }
+
   public boolean isValid() {
     return isValid;
   }