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

glass/src/lib/native/cpp/other/Log.cpp

@@ -5,7 +5,6 @@
 #include "glass/other/Log.h"
 
 #include <imgui.h>
-#include <wpi/raw_ostream.h>
 
 using namespace glass;
 
@@ -17,14 +16,13 @@ void LogData::Clear() {
   m_lineOffsets.push_back(0);
 }
 
-void LogData::Append(const wpi::Twine& msg) {
+void LogData::Append(std::string_view msg) {
   if (m_lineOffsets.size() >= m_maxLines) {
     Clear();
   }
 
   size_t oldSize = m_buf.size();
-  wpi::raw_string_ostream os{m_buf};
-  msg.print(os);
+  m_buf.append(msg);
   for (size_t newSize = m_buf.size(); oldSize < newSize; ++oldSize) {
     if (m_buf[oldSize] == '\n') {
       m_lineOffsets.push_back(oldSize + 1);