Venue request form: use API 2 to submit a request for service

[melisabok]

Program chairs should start using API 2 to submit the request to create a new venue.

• We should create the invitation and the group using API 2.
• Migrate all the stages to API 2 invitations
• Show all the API 2 stage invitations in the group editor or venue management UI
• Show all the API 2 recruitment and setup matching invitations in the group editor or venue management UI

[melisabok]

I will be creating other issues to specify the migration of the stages and recruitment invitations.

[melisabok]

It depends on https://github.com/openreview/openreview-py/issues/1890