Make work item payload smaller for crossgen-comparison job

[jkoritzinsky]

We currently put up the whole artifacts directory as the work item for our crossgen comparison jobs. This results in a massive work item which the ARM machines sometimes have trouble downloading according to #33404 (comment). We should instead create a separate folder that has only the necessary files and send that as the work item directory to save space over the wire and speed up the download.

cc: @jashook

[jashook]

Looks like our core_root directory is pretty large in general. It is almost 1g

[jashook]

I will open a second issue to improve the size of the workitem for all helix submissions. I believe this should be looked at now that so much has changed over the last few months.