Merge #13877: utils: Make fs::path::string() always return utf-8 string on Windows

2c3eade704 Make fs::path::string() always return utf-8 string (Chun Kuan Lee)

Pull request description:

  Imbue `fs::path` with `std::codecvt_utf8_utf16` at `SetupEnvironment()`, so that default string encoding will be utf-8 inside `fs::path`.

Tree-SHA512: 0cb59464d777278decbf24771fc5ff0cb2caa7bc2fe8ee5cd36c97a2324873a3caad131f08f050393b488316ee7f4ab0b28b7fa4699e41839f8e51b9867d5118

test/lint/lint-includes.sh

@@ -54,7 +54,6 @@ EXPECTED_BOOST_INCLUDES=(
     boost/chrono/chrono.hpp
     boost/date_time/posix_time/posix_time.hpp
     boost/filesystem.hpp
-    boost/filesystem/detail/utf8_codecvt_facet.hpp
     boost/filesystem/fstream.hpp
     boost/multi_index/hashed_index.hpp
     boost/multi_index/ordered_index.hpp