Move `ChainChecks` into tests

[lehins]

Thanks to integration done in IntersectMBO/ouroboros-consensus#2043 we no longer need this module, since it was only needed for Consensus: https://github.com/IntersectMBO/cardano-ledger/blob/ebed62de1ebcd4b13512418d49d17802a193e2c1/eras/shelley/impl/src/Cardano/Ledger/Chain.hs

It is still needed for testing, so we should move it to the only place in ledger where it is actually used.