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/include/frc/Watchdog.h

@@ -5,10 +5,10 @@
 #pragma once
 
 #include <functional>
+#include <string_view>
 #include <utility>
 
 #include <units/time.h>
-#include <wpi/StringRef.h>
 
 #include "frc/Tracer.h"
 
@@ -76,7 +76,7 @@ class Watchdog {
    *
    * @param epochName The name to associate with the epoch.
    */
-  void AddEpoch(wpi::StringRef epochName);
+  void AddEpoch(std::string_view epochName);
 
   /**
    * Prints list of epochs added so far and their times.