Ensure ci_pipelines.iid set before transaction in commit status API

What does this MR do and why?

Prior to this we were using create! which triggered the ensure_project_iid! in a callback. This causes a CrossDatabaseModificationAcrossUnsupportedTablesError. To avoid this we will create the iid before saving. This is consistent with all other places we create pipelines.

This change still doesn't allow us to remove spec/requests/api/commit_statuses_spec.rb from the allowlist as there are other calls to project.ci_pipelines.create! in this file.

We need a more holistic solution for that which is being discussed in !75316 (merged) .

It's important to note that this changes the semantics of what happens when saving the pipeline fails. Previously it would rollback the changes to the internal_ids table but now that these have been moved out of the transaction this update to internal_ids will not be rolled back. This isn't such a bad thing because it's just incrementing a counter and worse case scenario we have gaps in iid. In some other parts of our application we do try to reset this internal_id but I find that doing this could be buggy and I don't see the benefit outweighing the cost.

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Related to #335814 (closed)