chore(autopilot): make auction post-processing db operations atomic

[mrnaveira]

Background

Currently, the post_processing function on the autopilot performs multiple database saving operations in parallel. While this is good for performance, it opens the door for database inconsistencies in case the autopilot restarts between database operations.

Ideally we would like all the database operations (specially storing the winners and reference scores) to be done atomically.

Details

More in detail, the database operations are in the post_processing function:

save_auction
save_solutions // affects the proposed_solutions table
save_competition // affects the settlement_scores
save_surplus_capturing_jit_order_owner
store_fee_policies

Acceptance criteria

All previously indicated database operations are done atomically. Ideally with minimal performance impact.

[squadgazzz]

With the current DB design, this would negatively impact the auction runloop performance. While this issue is pretty important, I don't think we can currently afford it.