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

wpilibNewCommands/src/main/native/cpp/frc2/command/CommandScheduler.cpp

@@ -4,6 +4,8 @@
 
 #include "frc2/command/CommandScheduler.h"
 
+#include <cstdio>
+
 #include <frc/RobotBase.h>
 #include <frc/RobotState.h>
 #include <frc/TimedRobot.h>
@@ -15,7 +17,6 @@
 #include <networktables/NetworkTableEntry.h>
 #include <wpi/DenseMap.h>
 #include <wpi/SmallVector.h>
-#include <wpi/raw_ostream.h>
 
 #include "frc2/command/CommandGroupBase.h"
 #include "frc2/command/CommandState.h"
@@ -65,7 +66,7 @@ static bool ContainsKey(const TMap& map, TKey keyToCheck) {
 
 CommandScheduler::CommandScheduler()
     : m_impl(new Impl), m_watchdog(frc::TimedRobot::kDefaultPeriod, [] {
-        wpi::outs() << "CommandScheduler loop time overrun.\n";
+        std::puts("CommandScheduler loop time overrun.");
       }) {
   HAL_Report(HALUsageReporting::kResourceType_Command,
              HALUsageReporting::kCommand2_Scheduler);

wpilibNewCommands/src/main/native/cpp/frc2/command/PrintCommand.cpp

@@ -4,13 +4,13 @@
 
 #include "frc2/command/PrintCommand.h"
 
-#include <wpi/raw_ostream.h>
+#include <fmt/format.h>
 
 using namespace frc2;
 
 PrintCommand::PrintCommand(std::string_view message)
-    : CommandHelper{
-          [str = std::string(message)] { wpi::outs() << str << "\n"; }, {}} {}
+    : CommandHelper{[str = std::string(message)] { fmt::print("{}\n", str); },
+                    {}} {}
 
 bool PrintCommand::RunsWhenDisabled() const {
   return true;