Motivation

Zebra's integration tests can't currently use configured Testnets as the testnet::Parameters aren't correctly serialized, so the TestChild.with_config() method isn't working correctly.

There are few TODOs related to this that should be addressed once correct serialization has been implemented (search for #8920 to find them).

Zebra's also currently setting the NU5 activation height to 100 on Regtest in test compilations or when the proptest-impl feature is selected, this is used by the Regtest submit_blocks_test(). It should be removed and the test should be updated to use a config with that NU5 activation height instead.