tests: Allocate space dynamically in p_bson_find.
tests: Allocate space dynamically in p_bson_find.

Instead of using a statically sized array on the stack, allocate
memory dynamically. This allows us to increase the number of keys for
testing purposes, beyond stack limits.

algernon/libmongo-client,algernon/libmongo-client,algernon/libmongo-client