tpcc: enable setting percentage of workload

[ZhouXing19]

I am using HammerDB to run TPCC against my oracle container and I'd like to run insert only workload. However, I found the percentage of each workload type seems to be not configurable.

Ideally, we support such syntax in the tcl file:

    # Set workload to only perform NEW_ORDER transactions (insert only)
    diset tpcc driver timed
    diset tpcc keyandthink false
    diset tpcc neword 100    ;# Set 100% of the workload to NEW_ORDER (insert operations)
    diset tpcc payment 0     ;# 0% for payment (update)
    diset tpcc orderstat 0   ;# 0% for order status (select)
    diset tpcc delivery 0    ;# 0% for delivery (update)
    diset tpcc slev 0        ;# 0% for stock level (select)