Rename the conflicts property for the bulk operation

The `conflicts` property name is a bit confusing, especially for the use case of not using [Automatic ID Generation](https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-index_.html#_automatic_id_generation) where it has to be set to `sequential`, accompanied also by `conflict-probability=0`.

We should consider renaming it to something more understandable e.g. `automatic-id-strategy`.

Locate the bulk operation configuration and all references to the `conflicts` property, then review how it interacts with `sequential`, `conflict-probability=0`, and Automatic ID Generation. A decision on the replacement name and the required scope is still needed; done would mean the chosen name is applied consistently without changing the operation's behavior.

Written by the indexing model from the issue text.