rvgo: Witness cmd saves witness & stateHash to json

[pcw109550]

Description

Make witness command save witness and statehash to json.

type WitnessOutput struct {
	Witness   []byte   `json:"witness"`
	StateHash [32]byte `json:"stateHash"`
}

Tests

Manually tested using the absolute prestate of op-program on riscv.

Command: ./asterisc witness --input prestate.json --output -
Output:

{
  "witness": "wOSi8Cm62dDmKt1OGwxlLrSznk6zE4ghp7evP1rfrXYAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAIGCAAAAAAAAAAAAAAAAB/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
  "stateHash": [
    3,
    33,
    111,
    220,
    74,
    123,
    253,
    76,
    113,
    96,
    250,
    148,
    109,
    27,
    254,
    69,
    29,
    19,
    255,
    50,
    218,
    73,
    102,
    9,
    254,
    24,
    53,
    82,
    130,
    185,
    16,
    198
  ]
}