Implement crypto/pbkdf2 with the OpenSSL/CNG backends

[qmuntal]

Some internal customers want to use PBKDF2 in compliance with the Microsoft crypto policy. This means using OpenSSL/CNG under the hood.

Go 1.24 will most likely move golang.org/x/crypto/pbkdf2 into the standard library package crypto/pbkdf2 (see the proposal). We should patch it so it uses OpenSSL/CNG under the hood. Note that those backends already support that algorithm.