beacon/engine, miner: fix testing_buildBlockV1 response (#34704)

Two fixes for `testing_buildBlockV1`:

1. Add `omitempty` to `SlotNumber` in `ExecutableData` so it is omitted
for pre-Amsterdam payloads. The spec defines the response as
`ExecutionPayloadV3` which does not include `slotNumber`.

2. Pass `res.fees` instead of `new(big.Int)` in `BuildTestingPayload` so
`blockValue` reflects actual priority fees instead of always being zero.

Corresponding fixture update: ethereum/execution-apis#783

Author: newmanifold

beacon/engine/gen_ed.go

@@ -99,7 +99,7 @@ type ExecutableData struct {
 	Withdrawals   []*types.Withdrawal `json:"withdrawals"`
 	BlobGasUsed   *uint64             `json:"blobGasUsed"`
 	ExcessBlobGas *uint64             `json:"excessBlobGas"`
-	SlotNumber    *uint64             `json:"slotNumber"`
+	SlotNumber    *uint64             `json:"slotNumber,omitempty"`
 }
 
 // JSON type overrides for executableData.

beacon/engine/types.go

@@ -360,5 +360,5 @@ func (miner *Miner) BuildTestingPayload(args *BuildPayloadArgs, transactions []*
 	if res.err != nil {
 		return nil, res.err
 	}
-	return engine.BlockToExecutableData(res.block, new(big.Int), res.sidecars, res.requests), nil
+	return engine.BlockToExecutableData(res.block, res.fees, res.sidecars, res.requests), nil
 }