unexpect sst ingestion in l0 even if there is no overlapped data #18865
Description
Bug Report
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Steps to reproduce
We have met SST ingested not to the bottom level in different scenarios while the newly ingested SST files are not overlap with any existing data. In some cases, the sst files are ingested into l0 and cause flow-control; while in other cases, the SST files are ingested to other file that triggers huge compaction and impact the tail latency.
The root cause is the compatition guard current only split SST file when its size exceed a certain threshold(see compaction-guard-min-output-file-size), so it is possible that there is a existing sst file at the bottom level with a huge range that can block any incoming sst from being ingested into the bottom level.