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/uv/Handle.h

@@ -10,10 +10,10 @@
 #include <cstdlib>
 #include <functional>
 #include <memory>
+#include <string_view>
 #include <utility>
 
 #include "wpi/Signal.h"
-#include "wpi/StringRef.h"
 #include "wpi/uv/Buffer.h"
 #include "wpi/uv/Error.h"
 #include "wpi/uv/Loop.h"
@@ -50,7 +50,7 @@ class Handle : public std::enable_shared_from_this<Handle> {
   /**
    * Get the name of the type of the handle.  E.g. "pipe" for pipe handles.
    */
-  StringRef GetTypeName() const noexcept {
+  std::string_view GetTypeName() const noexcept {
     return uv_handle_type_name(m_uv_handle->type);
   }