Garbage collected sstables created during incremental compaction are
deleted only at the end of the compaction, which increases the memory
footprint. This is inefficient, especially considering that the related
input sstables are released regularly during compaction.
This commit implements incremental release of GC sstables after each
output sstable is sealed. Unlike regular input sstables, GC sstables
use a different exhaustion predicate: a GC sstable is only released
when its token range no longer overlaps with any remaining input
sstable. This is because GC sstables hold tombstones that may shadow
data in still-alive overlapping input sstables; releasing them
prematurely would cause data resurrection.
Fixes#5563Closesscylladb/scylladb#28984
6ce0968960