Add tests to cover hashCode() method for java supported crypto key types

As per jcov code coverage there are missing cases for hashCode and the gap is commonly found for supported key algorithms in java.

For me, It could be better to have a Test against a serialized copy to address these cases,
Note: It should also cover all possible supported crypto providers too.

Ex:
KeyPair pair = keyGen.generateKeyPair();
PrivateKey privateKey = pair.getPrivate();
....
privateKey.equals(copy(privateKey))
privateKey.hashCode() == copy(privateKey).hashCode()