Add simple parts of Table.take and Table.drop functions to Database table

[GregoryTravis]

Pull Request Description

Implements database Table and Column take/drop, except While and Sample.

Additional features and optimizations are in #7614.

Checklist

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[radeusgd]

The overall structure looks good to me.

However I was very surprised to see union used as part of the implementation. IMO it is too heavy and creates too complex queries (essentially the whole subquery which itself can be complex will be duplicated for each sub range, that can grow the SQL by large).

I'd suggest to use OR conditions in the filter instead - then we still keep a single subquery for this.

Also, please add the test for consecutive dropping/taking of elements, i.e.:

t.take 5 . take 3
t.take 3 . take 5
t.drop 3 . drop 2
t.drop 2 . drop 3

I know with the current implementation it should work, but I'd like to make sure and ensure we don't regress this when implementing any optimizations in the future.

[radeusgd]

Looks all good.

If possible, I'd like to change the ordering of sort operation in the newly added tests.

[radeusgd]

Please also try adding an 'integration' test where we try to take and add_row_number after an aggregation, i.e.:

t0 = table_builder [["X", ["a", "b", "a", "c"]], ["Y", [1, 2, 4, 8]]]
t1 = t0.aggregate [Aggregate_Column.Group_By "X", Aggregate_Column.Sum "Y"]

t2 = t1.add_row_number
t3 = t1.take 2
t4 = t1.drop 1

I imagine the actual result may be non deterministic, we should just check if it is "sane" - e.g. the add_row_number row contains values 1, 2, 3 and take and drop return consistent rows i.e. subset of ["a", 5], ["b", 2], ["c", 8].

[GregoryTravis]

Aggregate test added.

[jdunkerley]

Couple of minor tweaks.

Otherwise LGTM 👍