Add hartid argument to cli.

[pawks]

It is currently assumed that the hartid being tested is 0. This should be an argument in the cli to enable testing harts with other hartid values.

[anonymousr007]

Hello @pawks, I am Rishabh, an undergraduate student in computer science in India. Can you elaborate a little bit more? I would like to make a pull request for this issue 😄

[pawks]

The configuration for the hart is taken from the config yaml supplied by the plugins in the riscv-config format. The format supports configurations for multiple cores(harts) like in the example here. Currently it is assumed that the hart being tested is hart0. This feature would allow the hard id to be specified from the cli.