Use force_index_repo task type for Zoekt schema_version bump reindexing

What does this MR do and why?

When Zoekt indexing is triggered by a schema_version bump (via RepoToReindexEventWorker), it should use the force_index_repo task type instead of the default index_repo. This ensures that when the schema version changes, repositories are fully force-reindexed on the Zoekt node, which is the correct behavior for schema version upgrades.

Previously, create_bulk_tasks was called without a task_type argument, defaulting to :index_repo. Originally, when we wrote this worker, we intended to do a reindex, but we missed passing task_type. The worker's name also suggests it is a reindex worker.

The tests are also updated to:

• Assert that created tasks use the force_index_repo task type
• Use force_index_repo tasks in the "pending tasks" test scenarios, since the deduplication filter (without_pending_tasks_of_type) is now scoped to force_index_repo

The tests also got some cleanup, using more consistent factory patterns (like :ready instead of state: :ready) and clearer assertions to verify the specific task types being created. This makes the code more maintainable and the intent clearer for future developers.

References

• Issue: #596529 (closed)

Screenshots or screen recordings

N/A — backend-only change

How to set up and validate locally

1. Make sure your Rails GDK is up
2. Delete all the zoekt_tasks from the Rails console just for the ease of verification.

Search::Zoekt::Task.delete_all

3. Bump schemaVersion. For eg: 2602
4. Run make build-unified
5. Run gdk restart gitlab-zoekt-indexer-development-1 gitlab-zoekt-indexer-development-2.
6. Check in the Rails console, you should see new zoekt_tasks with force_index_repo task_type.

Search::Zoekt::Task.force_index_repo

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