[fix][broker] Fix memory leak if entry exists in cache (apache#16996)

* feat:return true if entry exists in cache

* feat:return true if entry exists in cache

* chore: add comment

Co-authored-by: zhiyuanlei <zhiyuanlei@tencent.com>

Master Issue: apache#16979

### Motivation

PR apache#12258 made changes to OpAddEntry which causes a memory leak when the entry is already in the cache.

### Modifications

Modifications: Revert PR apache#12258 changes to OpAddEntry

### Documentation

- [x] `doc-not-needed`

managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/OpAddEntry.java

@@ -213,11 +213,8 @@ public void safeRun() {
             EntryImpl entry = EntryImpl.create(ledger.getId(), entryId, data);
             // EntryCache.insert: duplicates entry by allocating new entry and data. so, recycle entry after calling
             // insert
-            // Entry cache doesn't copy the data if entry already exist into the cache.
-            // Backlog read tries to add entry into cache which can try to add duplicate entry into cache.
-            if (ml.entryCache.insert(entry)) {
-                entry.release();
-            }
+            ml.entryCache.insert(entry);
+            entry.release();
         }
 
         PositionImpl lastEntry = PositionImpl.get(ledger.getId(), entryId);