set if a stream contributes to connection flow control

This depends on the version. In gQUIC, stream 1 and 3 don't contribute,
in IETF QUIC only stream 0 doesn't contribute.

internal/protocol/version.go

@@ -68,6 +68,17 @@ func (vn VersionNumber) CryptoStreamID() StreamID {
 	return 0
 }
 
+// StreamContributesToConnectionFlowControl says if a stream contributes to connection-level flow control
+func (vn VersionNumber) StreamContributesToConnectionFlowControl(id StreamID) bool {
+	if id == vn.CryptoStreamID() {
+		return false
+	}
+	if vn.isGQUIC() && id == 3 {
+		return false
+	}
+	return true
+}
+
 func (vn VersionNumber) isGQUIC() bool {
 	return vn > gquicVersion0 && vn <= maxGquicVersion
 }