fix: single partition in SortPreservingMergeExec don't take fetch #12109
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Which issue does this PR close?
Closes #.
Rationale for this change
When SortPreservingMergeExec has only one partition, it directly calls its input to get the result. Therefore, the fetch parameter in SortPreservingMergeExec will have no effect.
so this pr, I reuse the LimitStream in Limit to limit the fetch result in SortPreservingMergeExec.
What changes are included in this PR?
Are these changes tested?
yes, add test for this case
Are there any user-facing changes?