Upgrade job manager's index_query method to SA2.0

[jdavcs]

SQLAlchemy 2.0 compatibility upgrades. Ref #12541. Extracted from #16852.

Two notable edits:

1. Calling union() on a Select statement creates a CompoundSelect object; executing it will return tuples of column values, not models. This causes a problem because the method is expected to return models in all cases. To ensure the method always returns models (regardless of whether the union is called or not), I used aliased() to map the Job model to the CompoundSelect object.
2. The combination of UNION and ORDER BY causes problems in SQLite. More details here: SQLAlchemy 2.0 upgrades (part 4) #16852 (comment). Solution: instead of using the Job class to access the column collection, use Job only if workflow jobs have not been added to the statement (and UNION has not been applied). Otherwise use the subquery produced by the union.

I've restructured the method - I think it's easier to follow its query-building logic this way. But if that's not the case, I'll drop the last commit.

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• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.