[SPARK-59687][SQL] Use exists instead of find(...).isDefined/isEmpty in catalyst and SQL core

[uros-b]

What changes were proposed in this pull request?

Several places in catalyst and SQL core test for a matching node/element with find(pred) followed by an Option presence check. On TreeNode (and Scala collections) exists(pred) is the equivalent, returning the Boolean directly. This replaces the pattern in four spots:

• WindowExpression.hasWindowExpression: e.find(_.isInstanceOf[WindowExpression]).isDefined -> e.exists(...)
• AliasHelper.getAliasMap: a.child.find(_.isInstanceOf[AggregateExpression]).isEmpty -> !a.child.exists(...)
• Analyzer.ResolveSQLFunctions.hasSQLFunctionExpression: _.find(_.isInstanceOf[SQLFunctionExpression]).nonEmpty -> _.exists(...)
• V2TableRefreshUtil.containsCommand: plan.find(_.isInstanceOf[Command]).isDefined -> plan.exists(...)

Why are the changes needed?

find(pred).isDefined / find(pred).nonEmpty are equivalent to exists(pred), and find(pred).isEmpty to !exists(pred) -- the same short-circuiting traversal, but find allocates an Option for the first match only for it to be discarded by the presence check. exists returns the Boolean directly and reads more clearly. Behavior is unchanged.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Existing tests. This is a behavior-preserving refactor; the catalyst and sql (core) modules compile cleanly.

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

Generated-by: Claude Code (Opus 4.8)

[uros-b]

This should be good to go, I don't think there are any additional occurrences in sql catalyst / core