Misc clang 21 fixes

* Use -O3 and other flags instead of -Ofast
  - https://discourse.llvm.org/t/rfc-deprecate-ofast/78687
  - https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
* Find libunwind library based on C++ compiler type, not C compiler type
* In stack_trace.cpp, pass stream modifiers to `std::stringstream` first, then send string to log
* In stack_trace.cpp, remove dead code related to `stack_trace_log` path
* Remove `virtual` method attributues from `final` class `cryptonote::core`
* Remove unused `this` capture in cryptonote protocol handler
* Remove unused variable `bad` in net node
* Use `std::make_unsigned` instead of `boost::make_unsigned`
  - https://github.com/boostorg/type_traits/issues/171
  - https://github.com/boostorg/type_traits/issues/202
  - https://github.com/boostorg/type_traits/pull/199
* Cleanup `include`s in pair serialization
* Test convergence b/t `std::make_unsigned` and `boost::make_unsigned`

Fixes compilation and silences warnings on:
clang version 21.1.6
Linux 6.18.8-3-cachyos

src/common/stack_trace.cpp

@@ -35,6 +35,7 @@
 
 #include <stdexcept>
 #include <iomanip>
+#include <sstream>
 #ifdef USE_UNWIND
 #define UNW_LOCAL_ONLY
 #include <libunwind.h>
@@ -54,7 +55,9 @@
   do { \
     auto elpp = ELPP; \
     if (elpp) { \
-      CINFO(el::base::Writer,el::base::DispatchAction::FileOnlyLog,MONERO_DEFAULT_LOG_CATEGORY) << x; \
+      std::stringstream ss; \
+      ss << x; \
+      CINFO(el::base::Writer,el::base::DispatchAction::FileOnlyLog,MONERO_DEFAULT_LOG_CATEGORY) << ss.str(); \
     } \
     else { \
       std::cout << x << std::endl; \
@@ -105,19 +108,9 @@ void CXA_THROW(void *ex, CXA_THROW_INFO_T *info, void (*dest)(void*))
   __real___cxa_throw(ex, info, dest);
 }
 
-namespace
-{
-  std::string stack_trace_log;
-}
-
 namespace tools
 {
 
-void set_stack_trace_log(const std::string &log)
-{
-  stack_trace_log = log;
-}
-
 void log_stack_trace(const char *msg)
 {
 #ifdef USE_UNWIND
@@ -127,7 +120,6 @@ void log_stack_trace(const char *msg)
   unsigned level;
   char sym[512], *dsym;
   int status;
-  const char *log = stack_trace_log.empty() ? NULL : stack_trace_log.c_str();
 #endif
 
   if (msg)