add compaction controller + simulator

Signed-off-by: Alex Chi Z <iskyzh@gmail.com>

mini-lsm/src/compact/leveled.rs

@@ -0,0 +1,25 @@
+use crate::lsm_storage::LsmStorageInner;
+
+pub struct LeveledCompactionTask {
+    upper_level: usize,
+    upper_level_sst_ids: Vec<usize>,
+    lower_level: usize,
+    lower_level_sst_ids: Vec<usize>,
+}
+
+pub struct LeveledCompactionController {}
+
+impl LeveledCompactionController {
+    pub fn generate_compaction_task(&self, snapshot: &LsmStorageInner) -> LeveledCompactionTask {
+        unimplemented!()
+    }
+
+    pub fn apply_compaction_result(
+        &self,
+        snapshot: &LsmStorageInner,
+        task: &LeveledCompactionTask,
+        output: &[usize],
+    ) -> (LsmStorageInner, Vec<usize>) {
+        unimplemented!()
+    }
+}