[runner][reporter] Report progress

[at15]

Runner should report the overall progress of the benchmark so user can have an estimation, i.e. when limit by time 10% 1s/10s, when limit by points 10% 1M/100M (numbers should be human readable when print to console, it's hard to count the zeros ...)

• have multiple reporter for progress, this is different from the reporter for worker results
• write to terminal
  • by time
  • by percentage
• expose to http handler?
• (optional) report to xephon-b central for distributed processing? then xephon-b itself becomes a framework runs inside benchhub's job scheduler