Add current/next slot timestamp to `get_status`

[aoudiamoncef]

Actually(testnet18), frontend devs have to calculate the next cycle timestamp based on current cycle:

        "version": "TEST.18.0",
        "current_time": 1674125023084,
        "current_cycle": 651,

Expected:

        "version": "TEST.18.0",
        "current_time": 1674125023084,
        "current_cycle": 651,
        "current_cycle_time": 1674125013084,
        "next_cycle_time": 1674125033084,