(fix) mpz has no attribute to_bytes py311

[MementoRC]

When running test_keypais.py, I get:

FAILED test/test_keypair.py::KeyPairTestCase::test_create_ecdsa_keypair_mnemonic - AttributeError: 'mpz' object has no attribute 'to_bytes'
FAILED test/test_keypair.py::KeyPairTestCase::test_create_ecdsa_keypair_uri - AttributeError: 'mpz' object has no attribute 'to_bytes'
FAILED test/test_keypair.py::KeyPairTestCase::test_sign_and_verify_ecdsa - AttributeError: 'mpz' object has no attribute 'to_bytes'
FAILED test/test_keypair.py::KeyPairTestCase::test_sign_and_verify_invalid_signature_ecdsa - AttributeError: 'mpz' object has no attribute 'to_bytes'
FAILED test/test_keypair.py::KeyPairTestCase::test_sign_and_verify_public_ethereum_address - AttributeError: 'mpz' object has no attribute 'to_bytes'

It seems to be due to BIP32_CURVE.order() not being an int. It is also an issue with the x() and y() returns

[MementoRC]

@arjanz This is needed for the conda recipe: conda-forge/staged-recipes#23812 to pass the tests, any chances to review and assess if there is a better resolution?