crypto: restrict PBKDF2 args to signed int
OpenSSL internally represents the output length and the iteration count as signed integers, which is why node's C++ implementation expects these arguments to fit into signed integers as well. The JavaScript validation logic, however, only requires the arguments to be unsigned 32-bit integers, which is a superset of non-negative (signed) 32-bit integers.
Change the JavaScript validation to match the expectation within C++.