Capture balance diffs caused by beacon chain withdrawals

[weiihann]

Is your feature request related to a problem? Please describe.
I was doing an analysis on how frequent the state changes. The result is inaccurate as the balance diffs caused by beacon chain withdrawals aren't captured anywhere in the dataset (specifically the balance_diffs dataset).

Describe the solution you'd like
Add a new dataset for balance diffs from beacon chain withdrawals or modify existing balance_diffs dataset