KDF_PBKDF2 tests libraries including unsupported operations

[koharin]

Hi.
I'm using cryptofuzz to test cryptographic libraries.

I recognized that when testing KDF_PBKDF2, it produces incorrect difference.
For example, KDF_PBKDF2 in libgmp, linux, mpdecimal, blst, libsodim, bearssl, trezor-firmware, openssl libraries don't support SHAKE digest.
However, cryptofuzz test KDF_PBKDF2 with SHAKE digest, so that it catches as result is not correct.

It would be better to filter out libraries with unsupported algorithms before testing algorithms.

Thank you for your works for Cryptofuzz.

[gilles-peskine-arm]

This is the same problem as #69. You need to return std::nullopt in your Module implementation when given an unsupported or invalid input.

[koharin]

I'll add std::nullopt in module for unsupported input.
Thanks for your instruction.