[solver/protocol-smart-contracts] Integrate SaveDeal to Sovler

[narbs91]

General Description

As a developer I want to add the SaveDeal method to the apiv2.go module (part of #529) so that the solver can utilize this method to save deals on-chain

Which system(s) or functionality does this affect

This can be one or many. Please also include this in the title

solver, protocol-smart-contracts

Describe the changes, and how this affects/ interacts with each system.

1. Add the SaveDeal method to the apiv2 module
2. Update the solver code on match to call the SaveDeal
3. Update corresponding logic in the anura/job_offers endpoint
4. Ensure the solver code change is gated by the lilynext feature flag