Replace boost with C++17 std equivalents, upgrade LZ4 to 1.10.0

- boost::tuple → std::tuple (serialize.h, miner.cpp, script.cpp, walletdb.cpp)
- boost::shared_ptr → std::shared_ptr (trianglesrpc.cpp)
- boost::variant → std::variant for CTxDestination (script.h)
- boost::get → std::get_if (main.cpp, rpcblockchain.cpp, coincontroldialog.cpp, wallet.cpp)
- boost::apply_visitor → std::visit (base58.h, script.cpp, rpcwallet.cpp, test/base58_tests.cpp)
- boost::static_visitor removed from all visitor classes
- boost::lexical_cast → std::to_string/std::stoll (smessage.cpp, rpcsmessage.cpp)
- Removed unused boost/lexical_cast.hpp includes (rest.cpp, trianglesrpc.cpp)
- Removed boost/variant/get.hpp include (rpcdump.cpp)
- Upgraded vendored LZ4 from 1.1.3 to 1.10.0
- Updated LZ4_compress() → LZ4_compress_default() (smessage.cpp)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/rpcsmessage.cpp

@@ -5,7 +5,7 @@
 #include "main.h"
 #include "trianglesrpc.h"
 
-#include <boost/lexical_cast.hpp>
+#include <string>
 
 #include "smessage.h"
 #include "init.h" // pwalletMain
@@ -802,13 +802,13 @@ Value smsgbuckets(const Array& params, bool fHelp)
             {
                 std::set<SecMsgToken>& tokenSet = it->second.setTokens;
                 
-                std::string sBucket = boost::lexical_cast<std::string>(it->first);
+                std::string sBucket = std::to_string(it->first);
                 std::string sFile = sBucket + "_01.dat";
                 
                 snprintf(cbuf, sizeof(cbuf), "%"PRIszu, tokenSet.size());
                 std::string snContents(cbuf);
                 
-                std::string sHash = boost::lexical_cast<std::string>(it->second.hash);
+                std::string sHash = std::to_string(it->second.hash);
                 
                 nBuckets++;
                 nMessages += tokenSet.size();
@@ -849,8 +849,8 @@ Value smsgbuckets(const Array& params, bool fHelp)
         }; // LOCK(cs_smsg);
         
         
-        std::string snBuckets = boost::lexical_cast<std::string>(nBuckets);
-        std::string snMessages = boost::lexical_cast<std::string>(nMessages);
+        std::string snBuckets = std::to_string(nBuckets);
+        std::string snMessages = std::to_string(nMessages);
         
         Object objM;
         objM.push_back(Pair("buckets", snBuckets));
@@ -868,7 +868,7 @@ Value smsgbuckets(const Array& params, bool fHelp)
             
             for (it = smsgBuckets.begin(); it != smsgBuckets.end(); ++it)
             {
-                std::string sFile = boost::lexical_cast<std::string>(it->first) + "_01.dat";
+                std::string sFile = std::to_string(it->first) + "_01.dat";
                 
                 try {
                     boost::filesystem::path fullPath = GetDataDir() / "smsgStore" / sFile;