Use file handles directly instead of C file descriptors on Win32

[HertzDevil]

Resolves #14389.

This makes IO::FileDescriptor#@volatile_fd an Atomic(LibC::UIntPtrT) rather than an Atomic(LibC::HANDLE), to avoid breaking #fd's return type.

[Sija]

Could be shortened to:

Suggested change

	ORIGINAL_STDIN = IO::FileDescriptor.new(Crystal::System::FileDescriptor::STDIN_HANDLE, blocking: true)
	ORIGINAL_STDOUT = IO::FileDescriptor.new(Crystal::System::FileDescriptor::STDOUT_HANDLE, blocking: true)
	ORIGINAL_STDERR = IO::FileDescriptor.new(Crystal::System::FileDescriptor::STDERR_HANDLE, blocking: true)
	ORIGINAL_STDIN = IO::FileDescriptor.new(FileDescriptor::STDIN_HANDLE, blocking: true)
	ORIGINAL_STDOUT = IO::FileDescriptor.new(FileDescriptor::STDOUT_HANDLE, blocking: true)
	ORIGINAL_STDERR = IO::FileDescriptor.new(FileDescriptor::STDERR_HANDLE, blocking: true)

[HertzDevil]

Note to self: lib/reply/src/term_size.cr also defines LibC::STD_OUTPUT_HANDLE which should be dropped after this PR (this doesn't show up on CI because the interpreter is still disabled)