Cleanup v0 and v0.1 opportunity endpoints

[chouinar]

Summary

DO NOT DO THIS UNTIL WE HAVE CONFIRMED WITH HHS AND STAKEHOLDERS

Once we've finished launching v1 opportunities backed by a search index, the older opportunity endpoints can be removed. They have no direct users, so there is no issue deleting them. This will remove a lot of duplicate code, and help simplify our code base quite a bit.

Things to delete:

• https://github.com/HHS/simpler-grants-gov/tree/main/api/src/api/opportunities_v0
• https://github.com/HHS/simpler-grants-gov/tree/main/api/src/api/opportunities_v0_1
• https://github.com/HHS/simpler-grants-gov/tree/main/api/src/services/opportunities_v0
• https://github.com/HHS/simpler-grants-gov/tree/main/api/src/services/opportunities_v0_1
• https://github.com/HHS/simpler-grants-gov/tree/main/api/tests/src/api/opportunities_v0
• https://github.com/HHS/simpler-grants-gov/tree/main/api/tests/src/api/opportunities_v0_1
• https://github.com/HHS/simpler-grants-gov/blob/main/api/src/db/models/transfer/topportunity_models.py + generate migrations to remove this table
• https://github.com/HHS/simpler-grants-gov/blob/main/api/src/data_migration/copy_oracle_data.py - the script that loads data into the transfer table (Note there will be some infra we want to remove to no longer schedule this job as well)
• Factories updated (can remove transfer table)

This may be something we need to do in multiple PRs, especially regarding the DB tables to avoid anything breaking.

Acceptance criteria

• Verify there is no traffic to the old endpoints and notify consumers if there is.
• Code cleaned up