For performance reasons, I want to refactor the following classes:
- GlobalTxEntityMap
- Entity[MultiInstance]SynchronizationInterceptor
- EntityMultiInstanceInterceptor
- remove TxEntityMap as a class

* GlobalTxEntityMap

- two TransactionLocal variables for List and Set with identical contents of instances: list - for fast iteration, set - for fast contains().
Just List would be enough. It would be more efficient to have a variable in the EntityEnterpriseContext that would tell whether it is associated with a tx instead of using Set in GlobalTxEntityMap.

- in synchronize(Transaction tx) both the List and the Set a thrown out. It is innefficient but we have to do it in current impl.

Not to break stuff, I would create an interface for GlobalTxEntityMap and provide another implementation.

* EntitySynchronizationInterceptor

- in register(ctx, tx) we associate the ctx with TxEntityMap which is useless for this interceptor. It is used only for MultiInstance.

- I think we could avoid instantiation of a new InstanceSynchronization per instance and registering it with the tx. We already do it in GlobalTxEntityMap. The synchronization logic could be put in 4 singleton classes one for each commit option A, B, C and D. At sync time we would just call synchronize(ctx) on the appropriate implementation according to commit option.

* MultiInstance interceptors and TxEntityMap

TxEntityMap is misused. It should to be used only with MultiInstance interceptors and is meant to be a per-tx-instance-cache. So, ideally, it should be another InstanceCache implementation.

Any objections? Bless me.