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/script.h

@@ -11,7 +11,7 @@
 
 #include <stdint.h>
 
-#include <boost/variant.hpp>
+#include <variant>
 
 #include "keystore.h"
 #include "bignum.h"
@@ -52,7 +52,7 @@ public:
  *  * CScriptID: TX_SCRIPTHASH destination
  *  A CTxDestination is the internal data type encoded in a CTrianglesAddress
  */
-typedef boost::variant<CNoDestination, CKeyID, CScriptID> CTxDestination;
+typedef std::variant<CNoDestination, CKeyID, CScriptID> CTxDestination;
 
 const char* GetTxnOutputType(txnouttype t);