node,blocksync,config: remove support for running nodes with blocksync disabled (#7159)

We stopped testing these configurations a while ago, and it doesn't
really make sense to allow nodes to run in this configuration. This
drops support for non-blocksync nodes and cleans up the
configuration/tests accordingly.

Closes: #6908

test/e2e/pkg/testnet.go

@@ -84,7 +84,6 @@ type Node struct {
 	IP               net.IP
 	ProxyPort        uint32
 	StartAt          int64
-	BlockSync        string
 	Mempool          string
 	StateSync        string
 	Database         string
@@ -177,7 +176,6 @@ func LoadTestnet(file string) (*Testnet, error) {
 			ABCIProtocol:     Protocol(testnet.ABCIProtocol),
 			PrivvalProtocol:  ProtocolFile,
 			StartAt:          nodeManifest.StartAt,
-			BlockSync:        "v0",
 			Mempool:          nodeManifest.Mempool,
 			StateSync:        nodeManifest.StateSync,
 			PersistInterval:  1,
@@ -335,11 +333,6 @@ func (n Node) Validate(testnet Testnet) error {
 			}
 		}
 	}
-	switch n.BlockSync {
-	case "", "v0", "v2":
-	default:
-		return fmt.Errorf("invalid block sync setting %q", n.BlockSync)
-	}
 	switch n.StateSync {
 	case StateSyncDisabled, StateSyncP2P, StateSyncRPC:
 	default: