Task-level limit parameters

[rodneykinney]

Modify core_bench to only download the capsules that will be used. (The --limit option is not currently forwarded to the task initializer).

To actually pass this limit to the task on the CLI, you need to use -T limit=, so add that to the demo.sh scripts.

Alternative to #93

[mdarcy220]

The one thing that worries me about adding these params to the suite tasks is that it introduces a new potential source of discrepancies (where two runs on supposedly the "same" task have different task params). I think it would be ideal if we used the parent tasks for the single-task demos (e.g. core_bench, super, sqa instead of core_bench_validation, super_validation, sqa_dev), so we keep the configurable stuff in the parent tasks and the suite tasks represent a fully-specified/instantiated task configuration.

[mdarcy220]

Last I checked, inspect eval-set (and by extension astabench eval) cannot take a -T param (this was the original the reason for having the separate _validation and _test tasks)

[rodneykinney]

In my testing, the -T parameter was passed through to the task initializer

[jbragg]

Another reason we defined separate val/test tasks was that it wasn't possible to pass through different task params to different tasks