[SPARK-49940][CONNECT]Make 'limit n' in spark connect use executeCollect

[xieshuaihu]

What changes were proposed in this pull request?

Call executeCollect when the DataFrame is CollectLimitExec or CollectTailExec.

Why are the changes needed?

For limit execution, SparkPlan.executeCollect is more performant than SparkPlan.execute.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Existing tests

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

No