Introduce QuicUtils::InvertPerspective and refactor code to use it

gfe-relnote: quic perspective refactor, no behavior change
PiperOrigin-RevId: 255318447
Change-Id: I10a7cb3478382f851d3f5a1293a248918ec95844
diff --git a/quic/core/quic_stream_id_manager.cc b/quic/core/quic_stream_id_manager.cc
index 793ee6c..8b8ff90 100644
--- a/quic/core/quic_stream_id_manager.cc
+++ b/quic/core/quic_stream_id_manager.cc
@@ -402,8 +402,7 @@
 }
 
 Perspective QuicStreamIdManager::peer_perspective() const {
-  return (perspective() == Perspective::IS_SERVER) ? Perspective::IS_CLIENT
-                                                   : Perspective::IS_SERVER;
+  return QuicUtils::InvertPerspective(perspective());
 }
 
 QuicTransportVersion QuicStreamIdManager::transport_version() const {