Add support for generic istream in ZArchiveReader

[SSimco]

The purpose of this change is to allow reading from files that cannot be opened directly from C++ code.

For example, on Android, if you want to open files that are not located in the app's internal storage, you must use SAF.
With SAF, you obtain a file descriptor, which can then be passed to C++ for reading.

Here's an example:

#include <boost/iostreams/device/file_descriptor.hpp>
#include <boost/iostreams/stream_buffer.hpp>
#include <zarchive/zarchivereader.h>
#include <istream>

using namespace boost::iostreams;

std::string fileUri = "content://com.android.externalstorage.documents/...";

// Call Java code to open the file using SAF and return a raw file descriptor
int fd = openContentUri(fileUri);

stream_buffer<file_descriptor_source> sb(fd, close_handle);
auto zar = ZArchiveReader::OpenFromStream(std::make_unique<std::istream>(&sb));
// ...
delete zar;