build: vendor the Slamtec rplidar SDK in third_party

The repo is now self-contained: driver_rplidar compiles the SDK from
third_party/rplidar_sdk (Linux sources only, teardown delete[] bug fixed
in place), so a plain cmake configure needs no SDK path and no probing —
the XLIDAR_RPLIDAR_SDK_DIR option and external references are gone.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

third_party/rplidar_sdk/src/sl_udp_channel.cpp

@@ -0,0 +1,129 @@
+/*
+ * Slamtec LIDAR SDK
+ *
+ *  Copyright (c) 2014 - 2020 Shanghai Slamtec Co., Ltd.
+ *  http://www.slamtec.com
+ *
+ */
+ /*
+  * Redistribution and use in source and binary forms, with or without
+  * modification, are permitted provided that the following conditions are met:
+  *
+  * 1. Redistributions of source code must retain the above copyright notice,
+  *    this list of conditions and the following disclaimer.
+  *
+  * 2. Redistributions in binary form must reproduce the above copyright notice,
+  *    this list of conditions and the following disclaimer in the documentation
+  *    and/or other materials provided with the distribution.
+  *
+  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+  * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+  *
+  */
+
+#include "sl_lidar_driver.h"
+#include "hal/abs_rxtx.h"
+#include "hal/socket.h"
+
+
+namespace sl {
+	class UdpChannel : public IChannel
+	{
+	public:
+		UdpChannel(const std::string& ip, int port) : _binded_socket(rp::net::DGramSocket::CreateSocket()) {
+            _ip = ip;
+            _port = port;
+        }
+
+		bool bind(const std::string & ip, sl_s32 port)
+        {
+            _socket = rp::net::SocketAddress(ip.c_str(), port);
+            return true;
+        }
+
+        bool open()
+        {
+            if(!bind(_ip, _port))
+                return false;
+            return SL_IS_OK(_binded_socket->setPairAddress(&_socket));         
+        }
+
+        void close()
+        {
+            _binded_socket->dispose();
+            _binded_socket = NULL;
+        }
+        void flush()
+        {
+            clearReadCache();
+        }
+
+        sl_result waitForDataExt(size_t& size_hint, sl_u32 timeoutInMs)
+        {
+            u_result ans;
+            size_hint = 0;
+            ans = _binded_socket->waitforData(timeoutInMs);
+
+            switch (ans) {
+            case RESULT_OK:
+                size_hint = 1024; //dummy value
+                break;
+            }
+
+            return ans;
+        }
+
+        bool waitForData(size_t size, sl_u32 timeoutInMs, size_t* actualReady)
+        {
+            if (actualReady)
+                *actualReady = size;
+            return (_binded_socket->waitforData(timeoutInMs) == RESULT_OK);
+
+        }
+
+        int write(const void* data, size_t size)
+        {
+            return _binded_socket->sendTo(nullptr, data, size);
+        }
+
+        int read(void* buffer, size_t size)
+        {
+            size_t actualGet;
+
+            u_result ans = _binded_socket->recvFrom(buffer, size, actualGet);
+            if (IS_FAIL(ans)) return 0;
+            return actualGet;
+        
+        }
+
+        void clearReadCache() {
+            _binded_socket->clearRxCache();
+        }
+
+        void setStatus(_u32 flag){}
+        
+        int getChannelType() {
+            return CHANNEL_TYPE_UDP;
+        }
+
+	private:
+		rp::net::DGramSocket * _binded_socket;
+		rp::net::SocketAddress _socket;
+        std::string _ip;
+        int _port;
+	};
+
+    Result<IChannel*> createUdpChannel(const std::string& ip, int port)
+    {
+        return new  UdpChannel(ip, port);
+    }
+}