See #36550
This PR made 2 changes:
1. Introducing a prioritization mechanism, if
`dataCoord.compaction.taskPrioritizer` is set to `level`, compaction
tasks are always executed as the priority of L0>Mix>Clustering
2. `dataCoord.compaction.maxParallelTaskNum` now controls the
parallelism of executing tasks, not the task number of queue +
executing.
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Signed-off-by: Ted Xu <ted.xu@zilliz.com>