Introduce AllGroupHeadsCollectorManager

[gaobinlong]

Description

AllGroupHeadsCollectorManager in grouping package did not have until now a corresponding collector manager, this pr introduces one and switches TestAllGroupHeadsCollector to use search concurrency and move away from the deprecated search(Query, Collector) method.

Relates to #12892.

[github-actions]

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[javanna]

Thanks for opening this PR @gaobinlong ! I had a quick look and my observations are similar to those I had at #15557 (comment) . We are introducing a new public collector manager that is only used in tests code, while the grouping collector code (GroupingSearch) requires some rework to rely on collector managers. I wonder if we should start with working on that, which looks though involving, or simply update the test so that it no longer relies on a collector manager.

All in all an important longer term question is how are grouping users going to move from collectors to collector managers. Lucene should probably include the building blocks for them to do so, and we need to define which those are.