Use std::string_view and fmtlib across all libraries (#3402)

- Twine, StringRef, Format, and NativeFormatting have been removed
- Logging now uses fmtlib style formatting
- Nearly all uses of wpi::outs/errs have been replaced with fmt::print() or
std::puts()/std::fputs() (for unformatted strings).
- A wpi/fmt/raw_ostream.h header has been added to enable
fmt::print() with wpi::raw_ostream

wpilibc/src/main/native/cpp/Tracer.cpp

@@ -4,7 +4,7 @@
 
 #include "frc/Tracer.h"
 
-#include <wpi/Format.h>
+#include <fmt/format.h>
 #include <wpi/SmallString.h>
 #include <wpi/raw_ostream.h>
 
@@ -25,7 +25,7 @@ void Tracer::ClearEpochs() {
   m_epochs.clear();
 }
 
-void Tracer::AddEpoch(wpi::StringRef epochName) {
+void Tracer::AddEpoch(std::string_view epochName) {
   auto currentTime = hal::fpga_clock::now();
   m_epochs[epochName] = currentTime - m_startTime;
   m_startTime = currentTime;
@@ -48,11 +48,9 @@ void Tracer::PrintEpochs(wpi::raw_ostream& os) {
   if (now - m_lastEpochsPrintTime > kMinPrintPeriod) {
     m_lastEpochsPrintTime = now;
     for (const auto& epoch : m_epochs) {
-      os << '\t' << epoch.getKey() << ": "
-         << wpi::format(
-                "%.6f",
-                duration_cast<microseconds>(epoch.getValue()).count() / 1.0e6)
-         << "s\n";
+      os << fmt::format(
+          "\t{}: {:.6f}s\n", epoch.getKey(),
+          duration_cast<microseconds>(epoch.getValue()).count() / 1.0e6);
     }
   }
 }