Avoid repetition in tests for serialize+deserialize tests

[ItsDrike]

We should add something into tests/helpers.py to help automatize testing serialization and deserialization, as we often end up making tests like test_uuid_serialize and test_uuid_deserialize, which are parametrized over the same exact arguments, (values data for creation, and expected data from serialization, or input data for deserialization and expected values).

Instead, there should be a way to only specify these once, avoiding a lot of repetition, as both types and packets all need serialize and deserialize tests.