core, eth/catalyst: fix race conditions in tests (ethereum#26790)

Fixes a race in TestNewPayloadOnInvalidTerminalBlock where setting the TTD raced with
the miner. Solution: set the TTD on the blockchain config not the genesis config.

Also fixes a race in CopyHeader which resulted in race reports all over the place.

Author: MariusVanDerWijden

core/types/block.go

@@ -279,6 +279,7 @@ func CopyHeader(h *Header) *Header {
 		copy(cpy.Extra, h.Extra)
 	}
 	if h.WithdrawalsHash != nil {
+		cpy.WithdrawalsHash = new(common.Hash)
 		*cpy.WithdrawalsHash = *h.WithdrawalsHash
 	}
 	return &cpy

eth/catalyst/api_test.go

@@ -874,7 +874,7 @@ func TestNewPayloadOnInvalidTerminalBlock(t *testing.T) {
 	n, ethservice := startEthService(t, genesis, preMergeBlocks)
 	defer n.Close()
 
-	genesis.Config.TerminalTotalDifficulty = preMergeBlocks[0].Difficulty() //.Sub(genesis.Config.TerminalTotalDifficulty, preMergeBlocks[len(preMergeBlocks)-1].Difficulty())
+	ethservice.BlockChain().Config().TerminalTotalDifficulty = preMergeBlocks[0].Difficulty() //.Sub(genesis.Config.TerminalTotalDifficulty, preMergeBlocks[len(preMergeBlocks)-1].Difficulty())
 
 	var (
 		api    = NewConsensusAPI(ethservice)