Replace std::snprintf() with wpi::format_to_n_c_str() (#5645)

fmtlib uses consteval format string processing, which makes it more
efficient than std::snprintf().

snprintf()s in libuv, mpack, processstarter, and wpigui were left alone.
processstarter uses stdlib only, and wpigui only depends on imgui.

fmt::format_to_n() is analogous to std::format_to_n()
(https://en.cppreference.com/w/cpp/utility/format/format_to_n)

wpi::format_to_n_c_str() is a wrapper which adds the trailing NUL.

wpilibc/src/main/native/cpp/smartdashboard/MechanismLigament2d.cpp

@@ -4,7 +4,7 @@
 
 #include "frc/smartdashboard/MechanismLigament2d.h"
 
-#include <cstdio>
+#include <wpi/StringExtras.h>
 
 using namespace frc;
 
@@ -36,8 +36,10 @@ void MechanismLigament2d::UpdateEntries(
 
 void MechanismLigament2d::SetColor(const Color8Bit& color) {
   std::scoped_lock lock(m_mutex);
-  std::snprintf(m_color, sizeof(m_color), "#%02X%02X%02X", color.red,
-                color.green, color.blue);
+
+  wpi::format_to_n_c_str(m_color, sizeof(m_color), "#{:02X}{:02X}{:02X}",
+                         color.red, color.green, color.blue);
+
   if (m_colorEntry) {
     m_colorEntry.Set(m_color);
   }