ARR: Enable SACs/ACs to add/remove others from commenting

[haroldrubio]

Resolves #2263

Depends on openreview-web#2133

This PR adds a new type to the ARRStage Commentary_Control and builds the invitations similar to how the registration forms are generated:

• Create a super invitation ARRCycle/-/Commentary_Control to store the process script
• For each submission, post an invitation for Commentary_Control_Form and post a note to that invitation
• Use this new note as the forum and reply to for the child invitations SubmissionX/-/Commentary_Control

Replies to the child invitation will modify fields in the SubmissionX/-/Official_Comment invitation

The super invitation does not have the invitation_edit_process date process function since the child invitations require an extra field in their edit content:

'responseForumId': {
    'value': {
        'param': {
            'type': 'string'
        }
    }
}

TODO:

• Prevent request form overwriting in specific cases
• Adjust wording/invitation names to make sense
• Simplify process function logic (was originally designed to add/remove reviewers as well)

Links in the consoles:

Forum page example: