Remove zombie stream map in QuicSession.

Those streams will live in stream_map_ instead.

This CL also removes some duplicated tests.

Protected by gfe2_reloadable_flag_quic_remove_zombie_streams

PiperOrigin-RevId: 324877471
Change-Id: I6d3df84048c35e7ca52ec030e019bbc0def4d3ce
diff --git a/quic/core/quic_stream.h b/quic/core/quic_stream.h
index 2a7d036..12b1192 100644
--- a/quic/core/quic_stream.h
+++ b/quic/core/quic_stream.h
@@ -203,6 +203,10 @@
   }
   bool write_side_closed() const { return write_side_closed_; }
 
+  bool IsZombie() const {
+    return read_side_closed_ && write_side_closed_ && IsWaitingForAcks();
+  }
+
   bool rst_received() const { return rst_received_; }
   bool rst_sent() const { return rst_sent_; }
   bool fin_received() const { return fin_received_; }