Reread ChangeData in email constructors

Email processing is often kicked off into a background thread, so it
is not safe to use the non-threadsafe accessors of Change. Rework the
ChangeEmail hierarchy so a new ChangeData is created in each
constructor, which ensures data is reread in a background thread. This
is a little slow, particularly as not all emails are sent async, but
is the best way we have of guaranteeing safety. It is also a little
ugly as the destination project/branch need to be passed to a super
constructor, and we can't have a statement creating this new
ChangeData prior to the super call, so the ChangeData needs to be
explicitly created in each leaf type.

Change-Id: Ibc549791e5cb2a23fbc4d7acca96589782757296

gerrit-server/src/main/java/com/google/gerrit/server/change/ChangeInserter.java

@@ -244,7 +244,7 @@ public class ChangeInserter {
         public void run() {
           try {
             CreateChangeSender cm =
-                createChangeSenderFactory.create(change);
+                createChangeSenderFactory.create(change.getId());
             cm.setFrom(change.getOwner());
             cm.setPatchSet(patchSet, patchSetInfo);
             cm.addReviewers(reviewers);