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.

glass/src/lib/native/cpp/hardware/PowerDistribution.cpp

@@ -5,9 +5,9 @@
 #include "glass/hardware/PowerDistribution.h"
 
 #include <algorithm>
-#include <cstdio>
 
 #include <imgui.h>
+#include <wpi/StringExtras.h>
 
 #include "glass/Context.h"
 #include "glass/DataSource.h"
@@ -36,7 +36,8 @@ static float DisplayChannel(PowerDistributionModel& pdp, int channel) {
 
 void glass::DisplayPowerDistribution(PowerDistributionModel* model, int index) {
   char name[128];
-  std::snprintf(name, sizeof(name), "PowerDistribution[%d]", index);
+  wpi::format_to_n_c_str(name, sizeof(name), "PowerDistribution[{}]", index);
+
   if (CollapsingHeader(name)) {
     // temperature
     if (auto tempData = model->GetTemperatureData()) {