* ScanQuery: equals/hashCode/toString
* DruidQuery: changes of Align ScanQuery column order with its desired signature #17457
* ScanQueryTest: add equalsverifer test
* introduces `UnionQuery`
* some changes to enable a `UnionQuery` to have multiple input datasources
* `UnionQuery` execution is driven by the `QueryLogic` - which could later enable to reduce some complexity in `ClientQuerySegmentWalker`
* to run the subqueries of `UnionQuery` there was a need to access the `conglomerate` from the `Runner`; to enable that some refactors were done
* renamed `UnionQueryRunner` to `UnionDataSourceQueryRunner`
* `QueryRunnerFactoryConglomerate` have taken the place of `QueryToolChestWarehouse` which shaves of some unnecessary things here and there
* small cleanup/refactors
Change the persona for errors within the planner from Admin to User. The ADMIN persona is meant to be "a persona who is interacting with admin APIs and understands Druid query concepts". This isn't an admin API, it's a query API. Low quality error messages being returned to the correct audience is better than hiding all error messages.
The errors that can be returned back can be user solvable, and other times requires a druid expert. But the errors do not leak information that should only be seen by more expert/privileged personas.
The original ADMIN persona showed some reticence to tag low-quality error messages with a USER persona. but it really does seem user-directed to me so USER to me would make sense.
* Update errorprone, mockito, jacoco, checkerframework.
This patch updates various build and test dependencies, to see if they
cause unit tests on JDK 21 to behave more reliably.
* Update licenses, tests.
* Remove assertEquals.
* Repair two tests.
* Update some more tests.
