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

ntcore/src/test/native/cpp/TestPrinters.h

@@ -7,15 +7,15 @@
 
 #include <memory>
 #include <ostream>
-
-#include <wpi/StringRef.h>
+#include <string>
+#include <string_view>
 
 #include "gtest/gtest.h"
 
 namespace wpi {
 
-inline void PrintTo(StringRef str, ::std::ostream* os) {
-  ::testing::internal::PrintStringTo(str.str(), os);
+inline void PrintTo(std::string_view str, ::std::ostream* os) {
+  ::testing::internal::PrintStringTo(std::string{str}, os);
 }
 
 }  // namespace wpi