core/vm: add bn256ScalarMul testcase for zero scalar value (#26607)

EIP-196 allows a zero value in the scalar argument to precompile `0x07`. This change adds a test for that case. 

core/vm/testdata/precompiles/bn256ScalarMul.json

@@ -124,5 +124,12 @@
     "Name": "cdetrio15",
     "Gas": 6000,
     "NoBenchmark": true
+  },
+  {
+    "Input": "039730ea8dff1254c0fee9c0ea777d29a9c710b7e616683f194f18c43b43b869073a5ffcc6fc7a28c30723d6e58ce577356982d65b833a5a5c15bf9024b43d980000000000000000000000000000000000000000000000000000000000000000",
+    "Expected": "00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+    "Name": "zeroScalar",
+    "Gas": 6000,
+    "NoBenchmark": true
   }
 ]
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