update bmk-driver arg parsing to allow more flexibility

This is simply a feature addition in getopt to support running benchmarks with their YAML keys as arguments.

This allows orchestrators to eliminate parsing logic on workload yaml keys. Instead of translating

args:
    events: 3
    threads: 1
    copies: 2

into -e 3 -t 1 -c 2, you can simply use the keys and values as the argument:

--events 3 --threads 1 --copies 2 (or --events=3 -t=1, -c 2, it supports all combinations)