Allow negative coinbase profit in Order::Tx and Order::Bundle

[liamaharon]

When disallowed for all Order varients, the coinbase account has no way to spend funds when rbuilder is building all blocks for a chain.

Instead of using saturating_sub, I also tried changing coinbase_profit from a U256 to an I256, but ran into issues where a U256 is required to calculate stuff like mev_gas_price in later logic. I'd prefer that approach if anyone knows if it is feasible.

[dvush]

Thanks! I think this is a good approach.

[github-actions]

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Date (UTC)	2024-11-01T13:27:02+00:00
Commit	3620348d2d7396d65ed353e6ac34a76f3c2308c0
Base SHA	e79af73510280e1bbb4de1ae19176d99ba0d104d

Significant changes

None