Incorrect prediction of validators count to be exited in ejector module

[rkolpakov]

Prediction service for ejector module was designed to predict protocol earnings based on [cl rewards withdrawals] (https://github.com/lidofinance/lido-oracle/blob/develop/src/services/prediction.py#L56) per report. If cl vault were filled up by a huge amount of ETH, protocol limits withdraw ETH amount, so prediction service operates not with income but with withdrawn ETH value.
Eject might start ejecting less validators than protocol requires to finalize withdrawal requests.

The suggestion is to get balance diff from simulation in order to obtain aligned protocol income.