Add sharding keys for feature category fuzz_testing

These tables have been identified as cell local tables.

All cell local tables require a sharding key.

A sharding key has been automatically selected for these tables. The sharding key was chosen because it is a NOT NULL column referencing either projects or namespaces.

Please confirm that this table should indeed be cell local, and that the selected column is an appropriate sharding key.

When updating the gitlab_schema we have also added allow_cross_joins, allow_cross_transactions and allow_cross_foreign_keys. You can read about this in https://docs.gitlab.com/ee/development/database/multiple_databases.html but basically for now we want to ignore any of these violations and just classify the tables that belong to gitlab_main_cell. In future we'll remove these allow_... statements so that we can fix these violations.

If you have any questions or concerns, reach out to @tigerwnz or @DylanGriffith.

This merge request was created using the gitlab-housekeeper gem.