C++20 Round 4: enum class TxnOutType, remove boost string alg, boost::int64_t -> int64_t

- txnouttype -> enum class TxnOutType (NonStandard, PubKey, PubKeyHash, ScriptHash, MultiSig)
  Updated script.h/cpp, main.cpp, wallet.cpp, rpcrawtransaction.cpp, rpcwallet.cpp, multisig_tests.cpp
- boost::int64_t/uint64_t -> int64_t/uint64_t across all RPC files (7 files, 52 replacements)
- Replace all boost string algorithm includes with std:: equivalents:
  - Added TrimString(), ToLower(), ReplaceAll(), SplitString(), JoinStrings() to util.h
  - boost::trim -> TrimString() (bootstrap.cpp, trianglesrpc.cpp, rest.cpp)
  - boost::to_lower -> ToLower() (netbase.cpp, trianglesrpc.cpp)
  - boost::split/is_any_of -> SplitString() (rpcdump.cpp, trianglesrpc.cpp, rest.cpp)
  - boost::replace_all -> ReplaceAll() (main.cpp, wallet.cpp)
  - boost::algorithm::starts_with/ends_with -> std::string::starts_with/ends_with (rpcdump.cpp, smessage.cpp)
  - boost::algorithm::istarts_with -> case-insensitive lambda (init.cpp, qtipcserver.cpp)
  - boost::algorithm::join -> JoinStrings() (util.cpp)
- boost::bind -> lambda in trianglesrpc.cpp async_accept handler
- IsHex() parameter: const string& -> string_view

src/netbase.cpp

@@ -13,7 +13,6 @@
 #endif
 
 #include "strlcpy.h"
-#include <boost/algorithm/string/case_conv.hpp> // for to_lower()
 
 using namespace std;
 
@@ -27,7 +26,7 @@ bool fNameLookup = false;
 static const unsigned char pchIPv4[12] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff };
 
 enum Network ParseNetwork(std::string net) {
-    boost::to_lower(net);
+    net = ToLower(net);
     if (net == "ipv4") return NET_IPV4;
     if (net == "ipv6") return NET_IPV6;
     if (net == "tor")  return NET_TOR;