TUN-4597: Add a QUIC server skeleton

- Added a QUIC server to accept streams
- Unit test for this server also tests ALPN
- Temporary echo capability for HTTP ConnectionType

vendor/github.com/lucas-clemente/quic-go/internal/flowcontrol/interface.go

@@ -0,0 +1,42 @@
+package flowcontrol
+
+import "github.com/lucas-clemente/quic-go/internal/protocol"
+
+type flowController interface {
+	// for sending
+	SendWindowSize() protocol.ByteCount
+	UpdateSendWindow(protocol.ByteCount)
+	AddBytesSent(protocol.ByteCount)
+	// for receiving
+	AddBytesRead(protocol.ByteCount)
+	GetWindowUpdate() protocol.ByteCount // returns 0 if no update is necessary
+	IsNewlyBlocked() (bool, protocol.ByteCount)
+}
+
+// A StreamFlowController is a flow controller for a QUIC stream.
+type StreamFlowController interface {
+	flowController
+	// for receiving
+	// UpdateHighestReceived should be called when a new highest offset is received
+	// final has to be to true if this is the final offset of the stream,
+	// as contained in a STREAM frame with FIN bit, and the RESET_STREAM frame
+	UpdateHighestReceived(offset protocol.ByteCount, final bool) error
+	// Abandon should be called when reading from the stream is aborted early,
+	// and there won't be any further calls to AddBytesRead.
+	Abandon()
+}
+
+// The ConnectionFlowController is the flow controller for the connection.
+type ConnectionFlowController interface {
+	flowController
+	Reset() error
+}
+
+type connectionFlowControllerI interface {
+	ConnectionFlowController
+	// The following two methods are not supposed to be called from outside this packet, but are needed internally
+	// for sending
+	EnsureMinimumWindowSize(protocol.ByteCount)
+	// for receiving
+	IncrementHighestReceived(protocol.ByteCount) error
+}