Adds the --aggregate option to the profile-instructions command.

For example. the aggregated trace of the sha256 benchmark is:

{
    "AluRRR": 5043,
    "Load": 4808,
    "Store": 2226,
    "LoadConst64": 2226,
    "LoadConst32": 1570,
    "Mov": 1465,
    "Shru64": 736,
    "Shl64": 625,
    "Call": 33,
    "Jal": 7,
    "ReserveSp": 5,
    "ReleaseSp": 5,
    "VirtualSPOffsetAdj": 2,
    "Icmp": 2,
    "CondBr": 2,
    "Ret": 2,
    "Args": 1
}

Context

We planned to have a discussion whether that kind of aggregation is useful. However, since work on zkwasm will be paused, I think it makes sense to commit this as is to wrap things up. In addition, the --aggregate option provides marginal value:

• Provide input data for further analysis/tools.
• Make total count per instruction easily available.