Simplify associative expressions with references

[tinfoil-knight]

Which issue does this PR close?

Draft for #11594

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Tests have been added.

Are there any user-facing changes?

Would be a breaking change for users relying on exact match of the optimized plan. Documentation doesn't need an update.

[tinfoil-knight]

For an expression like i + 1 + 2 which gets evaluated like (i + 1) + 2, we just need to re-arrange the grouping in Simplifier, so that the expression changes to i + (1 + 2).

In the subsequent run of the simplify, ConstEvaluator will resolve the arithmetic expression which only has literals now.

BinaryExpr(BinaryExpr { left: BinaryExpr(BinaryExpr { left: Column(Column { relation: None, name: "c3" }), op: Plus, right: Literal(Int32(1)) }), op: Plus, right: Literal(Int32(2)) })


BinaryExpr(BinaryExpr { left: Column(Column { relation: None, name: "c3" }), op: Plus, right: BinaryExpr(BinaryExpr { left: Literal(Int32(1)), op: Plus, right: Literal(Int32(2)) }) })
BinaryExpr(BinaryExpr { left: Column(Column { relation: None, name: "c3" }), op: Plus, right: Literal(Int32(3)) })

[tinfoil-knight]

Doesn't handle all possible positions currently for an associative expression.

Eg:

(i + 1) + 2; i + 1 + 2 will resolve to i + 3

But something like these won't
(1 + i) + 2
2 + (i + 1)
2 + (1 + i)
1 + 2 + i

[github-actions]

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