Investigate Clone performance

[rockfordlhotka]

Based on this thread (#4271) by @michaelcsikos, the Clone operation takes more than twice the time to do a data portal create/fetch operation.

This was confirmed by @rockfordlhotka in CSLA 9 by adding 10k child items to the PropertyPerf test app. The data portal create/fetch occurred in 2.8 seconds, the clone in 7.5 seconds.

The goal of this issue is to explore the way the clone occurs to see if there is any way to improve performance.

[StefanOssendorf]

I've started working on this.
My first finding is: Reverting #4333 increses the cloning performance by more than 50%.
But I suspect making the change for #4333 better/smarter will have a positive impact on all types of csla lists due to the identity management.

[StefanOssendorf]

I think I have a first win. Improving the speed by ~50% without breaking the relevant tests 🥳. But still more to do to get it down.

[luizfbicalho]

What is the status on this one?

[StefanOssendorf]

Still open and actionable. I did some stuff but nothing worth noting or merging.. So feel free to investigate :)