add compaction controller + simulator

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

mini-lsm/src/compact/tiered.rs

@@ -0,0 +1,23 @@
+use crate::lsm_storage::LsmStorageInner;
+use crate::table::SsTable;
+
+pub struct TieredCompactionTask {
+    tiers: Vec<usize>,
+}
+
+pub struct TieredCompactionController {}
+
+impl TieredCompactionController {
+    pub fn generate_compaction_task(&self, snapshot: &LsmStorageInner) -> TieredCompactionTask {
+        return TieredCompactionTask { tiers: Vec::new() };
+    }
+
+    pub fn apply_compaction_result(
+        &self,
+        snapshot: &LsmStorageInner,
+        task: &TieredCompactionTask,
+        output: &[usize],
+    ) -> (LsmStorageInner, Vec<usize>) {
+        (snapshot.clone(), Vec::new())
+    }
+}