### What changes were proposed in this pull request?
This PR updates the AQE framework to at least return one partition during coalescing.
This PR also updates `ShuffleExchangeExec.canChangeNumPartitions` to not coalesce for `SinglePartition`.
### Why are the changes needed?
It's a bit risky to return 0 partitions, as sometimes it's different from empty data. For example, global aggregate will return one result row even if the input table is empty. If there is 0 partition, no task will be run and no result will be returned. More specifically, the global aggregate requires `AllTuples` and we can't coalesce to 0 partitions.
This is not a real bug for now. The global aggregate will be planned as partial and final physical agg nodes. The partial agg will return at least one row, so that the shuffle still have data. But it's better to fix this issue to avoid potential bugs in the future.
According to https://github.com/apache/spark/pull/28916, this change also fix some perf problems.
### Does this PR introduce _any_ user-facing change?
no
### How was this patch tested?
updated test.
Closes#29307 from cloud-fan/aqe.
Authored-by: Wenchen Fan <wenchen@databricks.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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