Run process_builder_pending_payments before effective balance updates

[shane-moore]

Long form reasoning on this change in the discord chat

TLDR:
Move process_builder_pending_payments to run before process_effective_balance_updates in process_epoch. This makes compute_exit_epoch_and_update_churn use the current epoch effective balances, matching process_execution_payload behavior and avoiding inconsistent updates to state.exit_balance_to_consume and state.earliest_exit_epoch

[jtraglia]

Thanks @shane-moore, this change makes sense to me. We discussed this on the last ePBS breakout call and there was no real arguments against making this change. I believe potuz stated that he just added the call to the end of the function without much thought.