Move headers stream from 0 to 60 in v99

This CL also fixes a few tests that were incorrectly using the headers stream.

gfe-relnote: change header stream number, protected by v99 flag
PiperOrigin-RevId: 253691890
Change-Id: I1351cad387871efe39fb4387eac546e9a24efb7c
diff --git a/quic/core/quic_utils.cc b/quic/core/quic_utils.cc
index 996e78f..955e82f 100644
--- a/quic/core/quic_utils.cc
+++ b/quic/core/quic_utils.cc
@@ -399,6 +399,11 @@
 
 // static
 QuicStreamId QuicUtils::GetHeadersStreamId(QuicTransportVersion version) {
+  if (version == QUIC_VERSION_99) {
+    // TODO(b/130659182) Turn this into a QUIC_BUG once we've fully removed
+    // the headers stream in those versions.
+    return GetQuicFlag(FLAGS_quic_headers_stream_id_in_v99);
+  }
   return GetFirstBidirectionalStreamId(version, Perspective::IS_CLIENT);
 }