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

wpilibcExamples/src/main/cpp/examples/IntermediateVision/cpp/Robot.cpp

@@ -2,6 +2,7 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
+#include <cstdio>
 #include <thread>
 
 #include <cameraserver/CameraServer.h>
@@ -9,7 +10,6 @@
 #include <opencv2/core/core.hpp>
 #include <opencv2/core/types.hpp>
 #include <opencv2/imgproc/imgproc.hpp>
-#include <wpi/raw_ostream.h>
 
 /**
  * This is a demo program showing the use of OpenCV to do vision processing. The
@@ -18,7 +18,7 @@
  * processing.
  */
 class Robot : public frc::TimedRobot {
-#if defined(__linux__)
+#if defined(__linux__) || defined(_WIN32)
 
  private:
   static void VisionThread() {
@@ -60,12 +60,12 @@ class Robot : public frc::TimedRobot {
   void RobotInit() override {
     // We need to run our vision program in a separate thread. If not, our robot
     // program will not run.
-#if defined(__linux__)
+#if defined(__linux__) || defined(_WIN32)
     std::thread visionThread(VisionThread);
     visionThread.detach();
 #else
-    wpi::errs() << "Vision only available on Linux.\n";
-    wpi::errs().flush();
+    std::fputs("Vision only available on Linux or Windows.\n", stderr);
+    std::fflush(stderr);
 #endif
   }
 };

wpilibcExamples/src/main/cpp/examples/QuickVision/cpp/Robot.cpp

@@ -2,9 +2,10 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
+#include <cstdio>
+
 #include <cameraserver/CameraServer.h>
 #include <frc/TimedRobot.h>
-#include <wpi/raw_ostream.h>
 
 /**
  * Uses the CameraServer class to automatically capture video from a USB webcam
@@ -15,11 +16,11 @@
 class Robot : public frc::TimedRobot {
  public:
   void RobotInit() override {
-#if defined(__linux__)
+#if defined(__linux__) || defined(_WIN32)
     frc::CameraServer::GetInstance()->StartAutomaticCapture();
 #else
-    wpi::errs() << "Vision only available on Linux.\n";
-    wpi::errs().flush();
+    std::fputs("Vision only available on Linux or Windows.\n", stderr);
+    std::fflush(stderr);
 #endif
   }
 };