eth/catalyst: implement exchangeCapabilities method (#26555)

Spec: ethereum/execution-apis#364

eth/catalyst/api.go

@@ -79,6 +79,17 @@ const (
 	beaconUpdateWarnFrequency = 5 * time.Minute
 )
 
+// All methods provided over the engine endpoint.
+var caps = []string{
+	"engine_forkchoiceUpdatedV1",
+	"engine_forkchoiceUpdatedV2",
+	"engine_exchangeTransitionConfigurationV1",
+	"engine_getPayloadV1",
+	"engine_getPayloadV2",
+	"engine_newPayloadV1",
+	"engine_newPayloadV2",
+}
+
 type ConsensusAPI struct {
 	eth *eth.Ethereum
 
@@ -732,3 +743,8 @@ func (api *ConsensusAPI) heartbeat() {
 		}
 	}
 }
+
+// ExchangeCapabilities returns the current methods provided by this node.
+func (api *ConsensusAPI) ExchangeCapabilities([]string) []string {
+	return caps
+}