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/HttpWebSocketServerConnection.h

@@ -8,11 +8,11 @@
 #include <initializer_list>
 #include <memory>
 #include <string>
+#include <string_view>
 
 #include "wpi/ArrayRef.h"
 #include "wpi/HttpServerConnection.h"
 #include "wpi/SmallVector.h"
-#include "wpi/StringRef.h"
 #include "wpi/WebSocket.h"
 #include "wpi/WebSocketServer.h"
 #include "wpi/uv/Stream.h"
@@ -36,7 +36,7 @@ class HttpWebSocketServerConnection
    * @param protocols Acceptable subprotocols
    */
   HttpWebSocketServerConnection(std::shared_ptr<uv::Stream> stream,
-                                ArrayRef<StringRef> protocols);
+                                ArrayRef<std::string_view> protocols);
 
   /**
    * Constructor.
@@ -44,8 +44,9 @@ class HttpWebSocketServerConnection
    * @param stream network stream
    * @param protocols Acceptable subprotocols
    */
-  HttpWebSocketServerConnection(std::shared_ptr<uv::Stream> stream,
-                                std::initializer_list<StringRef> protocols)
+  HttpWebSocketServerConnection(
+      std::shared_ptr<uv::Stream> stream,
+      std::initializer_list<std::string_view> protocols)
       : HttpWebSocketServerConnection(
             stream, makeArrayRef(protocols.begin(), protocols.end())) {}
 
@@ -59,7 +60,7 @@ class HttpWebSocketServerConnection
    *
    * @param protocol negotiated subprotocol
    */
-  virtual bool IsValidWsUpgrade(StringRef protocol) { return true; }
+  virtual bool IsValidWsUpgrade(std::string_view protocol) { return true; }
 
   /**
    * Process an incoming WebSocket upgrade.  This is called after the header