KeyStore should have a getAttributes method

Currently the KeyStore.Entry.Attribute set for a keystore entry is only retrievable with Entry::getAttributes. This means for a PrivateKeyEntry that is protected with a password, you will have to provide that password to get the entry first to get the attributes.

This is not correct because the attributes was designed to be publicly available. A KeyStore::getAttributes method will suffice this purpose.

For example, in PKCS12, the attributes is out of the bag value. Therefore even if one cannot decrypt a pkcs8ShroudedKeyBag, the attributes set is still visible.