Run all maintenance/compaction tasks. Called periodically from the runtime event loop (idle maintenance) and on-demand via `PhysicalPlan::Compact`. When `force` is false (periodic), only compacts collections whose tombstone ratio exceeds the threshold. When `force` is true (on-demand), compacts everything. Per-database CPU budget is enforced when a budget tracker is installed. Collections whose
(&mut self, force: bool)
source not stored for this graph (policy: none)