Give an option to get a more precise termination penalty with pending termination penalty excluded

[jennijuju]

Termination sectors are triggered in a cron job and we patch them in several jobs when there is too may sector termination in one request. This means, with a new termination sector request, there might be some pending termination jobs left from the previous executed jobs that will be executed in this run as well.

The current lotus-shed sectors termination-estimation takes a list of sectors and calls terminate sectors and get the penalty without excluding the pending sectors. This may make the estimation a bit off if the miner has a lot of sectors termination in progress.

What we can do here is add an option to the cmd for getting a more accurate estimation. And to do so, we can sweep back from the current chain head until the tipset that miner does not have pending termination, then get the penalty for the sector termination requested.

[jennijuju]

related: #4617 (comment)