While working on CWallet, I noticed that it has methods that take a CChainParams as an argument but never use it. I removed those arguments. There is no other change than removing such parameters from function definitions and call-sites.
Now, the only remaining mention of CChainParams in those files is mostly related to CWallet::GetChainParams, which forwards the chain parameters from CWallet::m_chain
This is a follow-up to D7041.