Make crypto tests work with OpenSSL 3.0 under FIPS (#61)

There are a few restrictions enforced when OpenSSL 3.0 is used under
FIPS mode, that are incompatible with the Go tests, namely:

- For creating signature, encrypting, and decrypting, RSA key size
  must be equal to or longer than 2048 bits
- For verifying signature, RSA key size must be equal to or longer
  than 1024 bits
- PKCS#1 v1.5 is not supported for encryption and decryption (signing
  and verification are still allowed)

This either skips the relevant tests or increases key size used for
testing.

Signed-off-by: Daiki Ueno <[email protected]>

Signed-off-by: Daiki Ueno <[email protected]>