allow streams to marked as exhausted in more cases

At stream boundaries, we can mark streams as exhausted if there are no
groups active and there are no other ways to report matches. This allows us
to stop maintaining the history buffer on subsequent stream writes.
Previously, streams were only marked as exhausted if a pure highlander case
reported all patterns or the outfix in a sole outfix case died.

src/rose/rose_build_impl.h

@@ -601,6 +601,8 @@ public:
 
     u32 max_rose_anchored_floating_overlap;
 
+    rose_group boundary_group_mask = 0;
+
     QueueIndexFactory qif;
     ReportManager &rm;
     SomSlotManager &ssm;