revert to explicit bigint construction

op-challenger/game/fault/types/position.go

@@ -133,11 +133,11 @@ func (p Position) ToGIndex() *big.Int {
 
 // bigMSB returns the index of the most significant bit
 func bigMSB(x *big.Int) int {
-	if x.Cmp(new(big.Int)) == 0 {
+	if x.Cmp(big.NewInt(0)) == 0 {
 		return 0
 	}
 	out := 0
-	for ; x.Cmp(new(big.Int)) != 0; out++ {
+	for ; x.Cmp(big.NewInt(0)) != 0; out++ {
 		x = new(big.Int).Rsh(x, 1)
 	}
 	return out - 1

op-challenger/game/fault/types/types_test.go

@@ -4,7 +4,6 @@ import (
 	"math/big"
 	"testing"
 
-	"github.com/ethereum/go-ethereum/common"
 	"github.com/stretchr/testify/require"
 )
 
@@ -34,7 +33,7 @@ func TestIsRootPosition(t *testing.T) {
 	}{
 		{
 			name:     "ZeroRoot",
-			position: NewPositionFromGIndex(common.Big0),
+			position: NewPositionFromGIndex(big.NewInt(0)),
 			expected: true,
 		},
 		{

op-e2e/e2eutils/disputegame/helper.go

@@ -38,7 +38,7 @@ const alphabetGameDepth = 4
 var lastAlphabetTraceIndex = big.NewInt(1<<alphabetGameDepth - 1)
 
 // rootPosition is the position of the root claim.
-var rootPosition = faultTypes.NewPositionFromGIndex(common.Big1)
+var rootPosition = faultTypes.NewPositionFromGIndex(big.NewInt(1))
 
 type Status uint8