[SPARK-52311][SQL] Redefine UnionLoop output to not be duplicated if the anchor output is duplicated

[Pajaraja]

What changes were proposed in this pull request?

Redefine the output of the UnionLoop and UnionLoopRef to be with new expression IDs.

Why are the changes needed?

Currently rCTEs don't behave properly in case when the anchor references the same column multiple times in the anchor, leading to wrong things being identified in the recursion.
For example this rCTE:

WITH RECURSIVE tmp(x) AS (
values (1), (2), (3), (4), (5)
), rcte(x, y) AS (
SELECT x, x FROM tmp WHERE x = 1
UNION ALL
SELECT x + 1, x FROM rcte WHERE x < 5
)
SELECT * FROM rcte;

Will return:

1 1
2 2
3 3
4 4
5 5

Instead of:

1 1
2 1
3 2
4 3
5 4

Does this PR introduce any user-facing change?

No.

How was this patch tested?

New tests in golden file cte-recursion.sql.

Was this patch authored or co-authored using generative AI tooling?

No.

[cloud-fan]

nit: we can add a new apply method in object UnionLoop, which takes the same parameters as before, and pass anchor.output.map(_.newInstance().exprId) additionally to construct UnionLoop

[Pajaraja]

just using apply in object UnionLoop doesn't work because of default arguments.
in object UnionLoop, multiple overloaded alternatives of method apply define default arguments.
There are other possibilities to make this work, but I don't think any one change can work without modifying something in ResolveWithCTE.scala

[cloud-fan]

thanks, merging to master!