Pass chain params to ATMPArgs, LoadMempool, DisconnectedBlockTransactions::updateMempoolForReorg and CTxMemPool::removeForReorg because these objects only used the Config to access the chain params.
This enables removing the Config argument for a number of CChainstate member functions, since the chain params is now a member variable of CChainState after D12189.
I also remove the ATMPArgs argument from ConsensusScriptChecks, because it didn't use it.