Expose more fine-grained control over `find_objects` about rust-cryptoki HOT 4 OPEN

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One downside to the API above the mutable borrow means it is not possible to interleave calls to find_next with calls to other session operations. I think it's possible to recover that by adding a method session(&self) -> &Session to FindObjects. Since it only returns an & reference, it should be possible to do any other session operation except starting a new object search.

Also, I just realized that it would be necessary to change find_objects to take a mutable reference as well, to prevent someone from calling find_objects while another object search is ongoing. That would make this a breaking change.

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Another downside is that we can't handle errors from C_FindObjectsFinal, since it's called from drop. An alternative that would allow this is to use some sort of type-state: when we start a search, take the session by value, and then when you end the search you get the session back by value (only after checking for errors). One could still borrow a &Session during the search, to perform non-search operations.

I would consider this much less ergonomic than the API above. I doubt anyone cares much about handling errors from C_FindObjectsFinal, since there's not much you can do besides closing the session and trying to open a new one.

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The use-case is good and I like your ideas. 👍

While looking at your proposed API it makes a striking resemblance to the Iterator API. Just wondering, have you considered providing an interface like this? Of course then you'd have to return Option<Result<ObjectHandle>> (just like fallible iterators) and probably do some caching (so that FindObjects is not too frequently called).

PRs of course welcome! Sorry in advance for the delay in reviewing 🙇

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