Remove submitter from Domain Requests and Domain Info

[abroddrick]

Issue description

Creator will now be used to send emails (#2157) and at this point #2156 will have informed any user whose request is still active that their previous contact email (aka the submitter email) will no longer be used. We can now go ahead and just delete the submitter from Domain Request, Domain Info and any lingering places where it is still being used like unit tests, comments and fixtures

Acceptance criteria

• remove any contact associated with a submitter (this should be a migration file not a script)
• remove submitter from models (domain Request/domain info)
• remove submitter from references in comments and unit tests
• remove submitter from fixtures
• regenerate our database schema image without submitter in it
• remove any other reference to submitter not mentioned above

Additional context

No response

Links to other issues

• blocked by Change email sending to use Creator email not submitter on domain requests #2157
• blocked by Inform users who have different emails on their "submitter" vs user profile that further emails will go to the User profile email #2156
• once merged run this one: Run copy_names_from_contacts_to_users script on Stable #2285
• blocked by Conduct feature review for User profile feature #2327
• blocked by Stable: Turn profile flag on  #2408

[abroddrick]

marking this as blocked as we need to wait until the user profile feature is turned on. @vickyszuchin does product have a ticket for evaluating the profile ? We could block this one by that.

[vickyszuchin]

Removed "blocked". The dependencies on other tickets have been resolved.

[vickyszuchin]

This ticket was moved from sprint 51 to sprint 52 during Sprint 52 kickoff meeting.

[vickyszuchin]

Moved to current sprint (Sprint 53).