Use absl::visit instead of std::visit in quiche

std::visit doesn't interoperate with absl::variant in Chromium. Use absl::visit instead.

Also add a presubmit to prevent accidental addition of references to std::variant or std::visit in future.

No functional changes.

PiperOrigin-RevId: 518793885
diff --git a/quiche/quic/core/quic_stream_priority.h b/quiche/quic/core/quic_stream_priority.h
index b06f475..ca853e9 100644
--- a/quiche/quic/core/quic_stream_priority.h
+++ b/quiche/quic/core/quic_stream_priority.h
@@ -86,7 +86,7 @@
     }
   }
 
-  QuicPriorityType type() const { return std::visit(TypeExtractor(), value_); }
+  QuicPriorityType type() const { return absl::visit(TypeExtractor(), value_); }
 
   HttpStreamPriority http() const {
     if (absl::holds_alternative<HttpStreamPriority>(value_)) {