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

wpiutil/src/main/native/include/wpi/Hashing.h

@@ -53,6 +53,7 @@
 #include <cassert>
 #include <cstring>
 #include <string>
+#include <string_view>
 #include <utility>
 
 #ifdef _WIN32
@@ -660,6 +661,11 @@ hash_code hash_value(const std::basic_string<T> &arg) {
   return hash_combine_range(arg.begin(), arg.end());
 }
 
+template <typename T>
+hash_code hash_value(const std::basic_string_view<T> &arg) {
+  return hash_combine_range(arg.begin(), arg.end());
+}
+
 } // namespace wpi
 
 #ifdef _WIN32