add constructor for state compressor service

src/service/rooms/state_compressor.rs

@@ -72,6 +72,16 @@ impl CompressedStateEvent {
 }
 
 impl Service {
+    pub(crate) fn new(
+        db: &'static dyn Data,
+        stateinfo_cache_size: usize,
+    ) -> Self {
+        Self {
+            db,
+            stateinfo_cache: Mutex::new(LruCache::new(stateinfo_cache_size)),
+        }
+    }
+
     /// Returns a stack with info on shortstatehash, full state, added diff and
     /// removed diff for the selected shortstatehash and each parent layer.
     #[allow(clippy::type_complexity)]