feat: Reject orders with signed fee_amount != 0

[sunce86]

Problem

Starting from 19th of March (as stated in CIP38) orders with non-zero fee should be rejected by the protocol.

Suggested solution

Rejection means the orders with non-zero fees will no longer be settled by the protocol, implying:

1. Backend API needs to reject creation of new orders and return a specific error type in this case.
2. Existing open orders within the orderbook should be filtered out in solvable orders query (when autopilot auction is built).

Additional context

Market orders cleanup in all components can be done once this is released.

Acceptance criteria

POST-ing a new order with non-zero fee fails with specific error.

[harisang]

I wonder whether we can avoid (2) (i.e., open orders being ignored and rejected) by instead doing the following:

1. Decide on an activation block (some block after Tuesday March 19 midnight)
2. Prevent new fixed-fee orders to be created that have an expiration deadline after the block decided in (1). I suspect this should only affect orders being created the last few hours before activation of the CIP.

[sunce86]

Possibly duplicate of #2384.

Will keep the issue open as it contains more detailed info around implementation itself.