Clone identity objects to prevent races. (#15123)

changelog/15123.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+core: Fix some identity data races found by Go race detector (no known impact yet).
+```

vault/identity_store_entities.go

@@ -786,7 +786,7 @@ func (i *IdentityStore) mergeEntity(ctx context.Context, txn *memdb.Txn, toEntit
 			return errors.New("to_entity_id should not be present in from_entity_ids"), nil
 		}
 
-		fromEntity, err := i.MemDBEntityByID(fromEntityID, false)
+		fromEntity, err := i.MemDBEntityByID(fromEntityID, true)
 		if err != nil {
 			return nil, err
 		}

vault/identity_store_util.go

@@ -667,7 +667,7 @@ func (i *IdentityStore) processLocalAlias(ctx context.Context, lAlias *logical.A
 		return nil, fmt.Errorf("mount accessor %q is not local", lAlias.MountAccessor)
 	}
 
-	alias, err := i.MemDBAliasByFactors(lAlias.MountAccessor, lAlias.Name, false, false)
+	alias, err := i.MemDBAliasByFactors(lAlias.MountAccessor, lAlias.Name, true, false)
 	if err != nil {
 		return nil, err
 	}