Make ObjectReader/ObjectRangeReader compatible with io.Closer/io.ReaderCloser

[roman-khimov]

Consider nspcc-dev/neo-go#2995, there is an oracle subsystem that can do requests via HTTP and via NeoFS protocol. In the successful case we get some io.ReaderCloser for HTTP, but we have some really strange thing for NeoFS, it's io.Reader, but it's not io.ReaderCloser because its Close method returns some alien things. This means we can't unify some of the code for these cases even though they look very similar. Implementing proper io.Closer would be make for a much better library interface.

[cthulhu-rider]

can be done similar to #382 (comment)