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/fmt/raw_ostream.h

@@ -0,0 +1,30 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// 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.
+
+#ifndef WPIUTIL_WPI_FMT_RAW_OSTREAM_H_
+#define WPIUTIL_WPI_FMT_RAW_OSTREAM_H_
+
+#include "fmt/format.h"
+#include "wpi/raw_ostream.h"
+
+FMT_BEGIN_NAMESPACE
+
+inline void vprint(wpi::raw_ostream& os, string_view format_str,
+                   fmt::format_args args) {
+  memory_buffer buffer;
+  detail::vformat_to(buffer, format_str, args);
+  os.write(buffer.data(), buffer.size());
+}
+
+/**
+ * Prints formatted data to the stream *os*.
+ */
+template <typename S, typename... Args>
+void print(wpi::raw_ostream& os, const S& format_str, Args&&... args) {
+  vprint(os, format_str, fmt::make_args_checked<Args...>(format_str, args...));
+}
+
+FMT_END_NAMESPACE
+
+#endif  // WPIUTIL_WPI_FMT_RAW_OSTREAM_H_