allow setup matching between SACs and submissions

[celestemartinez]

We should allow SACs to be assigned to submissions as well, instead of only to ACs.

This are the changes to be made:

• add this as an option in the request form. This should allow the PCs to setup the paper matching between SACs and submissions (compute conflicts and affinity scores)
• add a property in the group.content about assigning ACs or submissions
• change the SAC console to load the AC tab when the property says they are assigning ACs.
• Create bid invitation for SACs to bid on papers (make this optional in bid stage form)
• Fix the deploy when SACs should be assigned to papers
• Fix any process functions that expect SACs to be assigned to ACs

@melisabok anything else missing?

Requires openreview/openreview-web#1876

[melisabok]

Create bid invitation for SACs to bid on papers

I'm not sure if we should make this optional in the BidStage form.

Missing:

1. add a property in the group.content about assigning ACs or submissions
2. change the SAC console to load the AC tab when the property says they are assigning ACs.

[celestemartinez]

Create bid invitation for SACs to bid on papers

I'm not sure if we should make this optional in the BidStage form.

I was planning on asking PCs in the bid stage form if they would like to enable it for SACs as well. I also don't think this should be the default.

Missing:

1. add a property in the group.content about assigning ACs or submissions
2. change the SAC console to load the AC tab when the property says they are assigning ACs.

I've added this two to the description. The first one is already done.