### What changes were proposed in this pull request?
This patch sorts equivalent expressions based on their child-parent relation.
### Why are the changes needed?
`EquivalentExpressions` maintains a map of equivalent expressions. It is `HashMap` now so the insertion order is not guaranteed to be preserved later. Subexpression elimination relies on retrieving subexpressions from the map. If there is child-parent relationships among the subexpressions, we want the child expressions come first than parent expressions, so we can replace child expressions in parent expressions with subexpression evaluation.
For example, we have two different expressions `Add(Literal(1), Literal(2))` and `Add(Literal(3), add)`.
Case 1: child subexpr comes first.
```scala
addExprTree(add)
addExprTree(Add(Literal(3), add))
addExprTree(Add(Literal(3), add))
```
Case 2: parent subexpr comes first. For this case, we need to sort equivalent expressions.
```
addExprTree(Add(Literal(3), add)) => We add `Add(Literal(3), add)` into the map first, then add `add` into the map
addExprTree(add)
addExprTree(Add(Literal(3), add))
```
As we are going to sort equivalent expressions at all, we don't need `LinkedHashMap` but just do sorting.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
Added tests.
Closes#32586 from viirya/use-listhashmap.
Authored-by: Liang-Chi Hsieh <viirya@gmail.com>
Signed-off-by: Liang-Chi Hsieh <viirya@gmail.com>
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