feat: Save auction data in parallel with competition

[sunce86]

Problem

Several auction related database tables are saved only after the competition is done. This is implemented like this, so that we avoid saving of auction data for auctions that did not have any solution reported (empty auctions are not useful). The second reason is also historical because we wanted to save only the prices and fee policies that were used in the competition (in the meantime we switched to saving all auction prices and will probably move to saving all fee policies).

Suggested solution

Saving of following auction related tables can happen in parallel with competition to save time. But then, we also need to delete auction data for auctions without solutions, and that can happen

1. After competition in a fire and forget manner, or
2. As a periodical db cleanup task

Affected tables:

1. auction_orders
2. auction_prices
3. surplus_capturing_jit_order_owners
4. fee_policies

Inspired by 200ms time spent for saving fee policies for all orders in the auction.

[squadgazzz]

The whole save_competition takes at most 250ms at the moment.

Since #3013 is merged, auction_orders and auction_prices should be executed in parallel. That would save us up to ~100ms only. Not a big win, actually.

[sunce86]

@squadgazzz Thanks for looking into it. This surely lowers the priority of the issue but I think we should tackle it eventually since it's a purely technical thing that delays runloop.

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