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/test/native/cpp/uv/UvGetAddrInfoTest.cpp

@@ -43,7 +43,7 @@ TEST(UvGetAddrInfo, BothNull) {
   });
 
   GetAddrInfo(
-      loop, [](const addrinfo&) { FAIL(); }, Twine::createNull());
+      loop, [](const addrinfo&) { FAIL(); }, "");
   loop->Run();
   ASSERT_EQ(fail_cb_called, 1);
 }