Support libzim9

[kelson42]

Unfortunately it fails because the getSize() of the iterator is now deprecated.

See https://github.com/openzim/node-libzim/actions/runs/7078395364/job/19263816211#step:6:2426

[kelson42]

@mgautierfr What should be the approach here?

[mgautierfr]

Is SearchIterator::getSize (the wrapped version) is used somewhere (by a tool using node-libzim) ?

If not (what I hope) we should simply remove it. Another approach is to mark the (wrapped) function as deprecated also and (either):

• Compile without -Werror to be able to use the deprecated libzim method.
• Reimplement the libzim method (return -1;)