Change the primary key of the to the billable usage remittance records to a UUID.

Done:

• every existing billable usage remittance DB record has a UUID populated
• new billable usage remittance records get UUIDs populated
• OpenAPI update - billable usage responses for `GET /internal/remittance/accountRemittances` updated to show the UUID WON'T DO
• QE should verify that billable usage responses have a UUID using the internal endpoint.
• Existing uniqueness constraint should be maintained
• If two phases are necessary (create & populate uuid column, and then make uuid column the primary key) then use this card for creating/populating the column and create a 2nd card for switching the primary key. 
• Rollout plan needs to make sure this work does not try to deploy while billable usage is being calculated. 
• This will need a IQE branch to support the API changes to include the UUID.