### What changes were proposed in this pull request?
By default, AQE will set `COALESCE_PARTITIONS_MIN_PARTITION_NUM` to the spark default parallelism, which is usually quite big. This is to keep the parallelism on par with non-AQE, to avoid perf regressions.
However, this usually leads to many small/empty partitions, and hurts performance (although not worse than non-AQE). Users usually blindly set `COALESCE_PARTITIONS_MIN_PARTITION_NUM` to 1, which makes this config quite useless.
This PR adds a new config to set the min partition size, to avoid too small partitions after coalescing. By default, Spark will not respect the target size, and only respect this min partition size, to maximize the parallelism and avoid perf regression in AQE. This PR also adds a bool config to respect the target size when coalescing partitions, and it's recommended to set it to get better overall performance. This PR also deprecates the `COALESCE_PARTITIONS_MIN_PARTITION_NUM` config.
### Why are the changes needed?
AQE is default on now, we should make the perf better in the default case.
### Does this PR introduce _any_ user-facing change?
yes, a new config.
### How was this patch tested?
new tests
Closes#33172 from cloud-fan/aqe2.
Authored-by: Wenchen Fan <wenchen@databricks.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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