When a mongocrypt_ctx_t is in the state MONGOCRYPT_CTX_NEED_MONGO_KEYS, the context provides a filter to query the key vault collection.

Currently, this filter will include an empty $in array for _id or keyAltNames in cases that one isn't necessary. E.g.

{"$or": [{"_id": {"$in": [ UUID(...) ] }}, {"keyAltName": {"$in": []}}]}

Instead, in cases where we have one or the other empty, we should simplify the filter:

{"_id": {"$in": [ UUID(...) ] }}}