Remove ghc/filesystem polyfill now that we are on C++17

[moxian]

Summary

Infrastructure "Remove ghc/filesystem polyfill"

Purpose of change

The ghc filesystem polyfill was introduced in #50624 back when we didn't have C++17.
Our min supported C++ version is C++17 now, so we can afford to remove it.

Fewer dependencies = good.

Describe the solution

Replace ghc/fs_std_fwd.hpp includes with includes of <filesystem>
Replace the fs::symbol occurences with std::filesystem::symbol
Remove the src/third-party/ghc dir
Check for ghc occurences in other places (LICENSE, clang-tidy) and remove those if applicable.

Describe alternatives you've considered

N/A

Testing

Game and tests compile and run.

CI should pass if I done everything right. (Hopefully android build isn't going to yell at me)

Additional context

[github-actions]

Auto-requesting reviews from non-collaborators: @jbytheway

[github-actions]

Remaining comments which cannot be posted as a review comment to avoid GitHub Rate Limit

[JSON & C++ formatters](https://github.com/CleverRaven/Cataclysm-DDA/blob/master/doc/DEVELOPER_TOOLING.md)

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/src/flexbuffer_cache.h

Line 55 in e770d13

explicit flexbuffer_cache( const std::filesystem::path &cache_directory, const std::filesystem::path &root_directory );

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/src/flexbuffer_cache.h

Line 59 in e770d13

static shared_flexbuffer parse( std::filesystem::path json_source_path, size_t offset = 0 ) noexcept( false );

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/src/tgz_archiver.cpp

Line 22 in e770d13

std::string tgz_archiver::_gen_tar_header( std::filesystem::path const &file_name, std::filesystem::path const &prefix,

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/src/tgz_archiver.cpp

Line 57 in e770d13

bool tgz_archiver::add_file( std::filesystem::path const &real_path, std::filesystem::path const &archived_path )

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/src/tgz_archiver.h

Line 18 in e770d13

std::string _gen_tar_header( std::filesystem::path const &file_name, std::filesystem::path const &prefix,

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/tests/monster_test.cpp

Lines 260 to 261 in e770d13

	data.open( std::filesystem::u8path( "slope_test_data_" + std::string( ( trigdist ? "trig_" : "square_" ) ) +
	monster_type ) );

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/tools/clang-tidy-plugin/test/u8-path.cpp

Line 8 in e770d13

static void call_fs_path_method( std::filesystem::path & ( std::filesystem::path::* method )( const char *const & ) )

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/tools/clang-tidy-plugin/test/u8-path.cpp

Line 118 in e770d13

std::filesystem::path &( std::filesystem::path::* fn_op_assign_path )( const std::filesystem::path & ) = &std::filesystem::path::operator=;

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/tools/clang-tidy-plugin/test/u8-path.cpp

Line 120 in e770d13

std::filesystem::path &( std::filesystem::path::* fn_op_assign_cstr )( const char *const & ) = &std::filesystem::path::operator=;

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/tools/clang-tidy-plugin/test/u8-path.cpp

Line 125 in e770d13

std::filesystem::path &( std::filesystem::path::* fn_assign_cstr )( const char *const & ) = &std::filesystem::path::assign;

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/tools/clang-tidy-plugin/test/u8-path.cpp

Lines 155 to 156 in e770d13

	static_cast<void>( static_cast<std::filesystem::path &( std::filesystem::path::* )( const char *const & )>
	( &path_inherit::assign ) );

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/tools/clang-tidy-plugin/test/u8-path.cpp

Lines 173 to 174 in e770d13

	static_cast<void>( static_cast<std::filesystem::path &( std::filesystem::path::* )( const char *const & )>
	( &path_using::operator= ) );

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[JSON & C++ formatters] _{reported by reviewdog 🐶}

Cataclysm-DDA/tools/clang-tidy-plugin/test/u8-path.cpp

Lines 176 to 177 in e770d13

	static_cast<void>( static_cast<std::filesystem::path &( std::filesystem::path::* )( const char *const & )>
	( &path_using::assign ) );

[moxian]

The clang-tidy error is real. I'll take a look in a bit...
The macos error is also real, but it might be better to fix in a separate PR.

[akrieger]

I kinda liked having ghc filesystem because I could trivially see the implementation of the various functions, but w/e.

[akrieger]

It would've been much cleaner to just do using fs = std::filesystem; everywhere which would preserve blame (and, selfishly, avoid rebase conflicts) better.

[moxian]

I don't think carrying around using fs = std::filesystem; forever just to preserve blame is a good idea. That's just legacy cruft that would need to go away away one day anyway.
I do sympathize with rebase woes though, sorry about that!

[akrieger]

We do go out of our way to reduce line thrash. This is a bit pedantic of a situation but no one would've objected to keeping it around. Especially because std::filesystem:: is quite mouthy.