chore(bb): lazy logging (#17164)

While working at C++ simulation optimization (ms granularity) I realized
that logging started to take a good chunk of time. This is especially
true now that builds use asserts (not `NDEBUG`) by default and there is
no "release" mode (and nobody will be using it).

The change in this PR makes the formatting of a log lazy for `debug` and
`vinfo`.

Author: fcarreiro

barretenberg/cpp/src/barretenberg/common/bb_bench.cpp

@@ -159,7 +159,7 @@ void print_separator(std::ostream& os, bool thick = true)
 {
     const char* line = thick ? "═══════════════════════════════════════════════════════════════════════════════════════"
                                "═════════════════════"
-                             : "───────────────────────────────────────────────────────────────────────────--------────"
+                             : "───────────────────────────────────────────────────────────────────────────────────────"
                                "─────────────────────";
     os << Colors::BOLD << Colors::CYAN << line << Colors::RESET << "\n";
 }

barretenberg/cpp/src/barretenberg/common/log.hpp

@@ -2,6 +2,7 @@
 #include "barretenberg/env/logstr.hpp"
 #include "barretenberg/stdlib/primitives/circuit_builders/circuit_builders_fwd.hpp"
 #include <algorithm>
+#include <functional>
 #include <sstream>
 #include <string>
 #include <vector>
@@ -55,28 +56,33 @@ template <typename... Args> std::string benchmark_format(Args... args)
 }
 
 extern bool debug_logging;
+// In release mode (e.g., NDEBUG is defined), we don't compile debug logs.
 #ifndef NDEBUG
-template <typename... Args> inline void debug(Args... args)
+#define debug(...) debug_([&]() { return format(__VA_ARGS__); })
+#else
+#define debug(...) (void)0
+#endif
+
+// We take a function so that evaluation is lazy.
+inline void debug_(std::function<std::string()> func)
 {
-    // NDEBUG is used to turn off asserts, so we want this flag to prevent debug log spamming.
     if (debug_logging) {
-        logstr(format(args...).c_str());
+        logstr(func().c_str());
     }
 }
-#else
-template <typename... Args> inline void debug(Args... /*unused*/) {}
-#endif
 
 template <typename... Args> inline void info(Args... args)
 {
     logstr(format(args...).c_str());
 }
 
+#define vinfo(...) vinfo_([&]() { return format(__VA_ARGS__); })
+
 extern bool verbose_logging;
-template <typename... Args> inline void vinfo(Args... args)
+inline void vinfo_(std::function<std::string()> func)
 {
     if (verbose_logging) {
-        info(args...);
+        info(func());
     }
 }