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/cpp/uv/Process.cpp

@@ -10,7 +10,7 @@
 
 namespace wpi::uv {
 
-std::shared_ptr<Process> Process::SpawnArray(Loop& loop, const Twine& file,
+std::shared_ptr<Process> Process::SpawnArray(Loop& loop, std::string_view file,
                                              ArrayRef<Option> options) {
   // convert Option array to libuv structure
   uv_process_options_t coptions;
@@ -20,8 +20,8 @@ std::shared_ptr<Process> Process::SpawnArray(Loop& loop, const Twine& file,
     h.exited(status, signal);
   };
 
-  SmallString<128> fileBuf;
-  coptions.file = file.toNullTerminatedStringRef(fileBuf).data();
+  SmallString<128> fileBuf{file};
+  coptions.file = fileBuf.c_str();
   coptions.cwd = nullptr;
   coptions.flags = 0;
   coptions.uid = 0;