feat: Add max prev events config option, allowing adjusting limit for prev_events fetching

src/service/rooms/event_handler/mod.rs

@@ -1226,7 +1226,7 @@ impl Service {
                 .await
                 .pop()
             {
-                if amount > 100 {
+                if amount > services().globals.max_fetch_prev_events() {
                     // Max limit reached
                     warn!("Max prev event limit reached!");
                     graph.insert(prev_event_id.clone(), HashSet::new());