Add ref.finance Locust workload

[aborg-dev]

It would be useful to have Ref.Finance smart contract represented as the Locust workload as it is a good use-case that is also popular on other blockchains (e.g. Solana) making it a good comparison point.

References:

• Smart Contract: https://github.com/ref-finance/ref-contracts/tree/main/ref-exchange
• Example transaction: https://nearblocks.io/txns/BHUpNyyv8imZwZnV9pQCsTzwA4NMqRfBDJjJoLp2osP4?tab=overview

[aborg-dev]

cc #11808

[jaswinder6991]

Hey @Akashin, I am happy to help here if we can specify the scope a bit.

Would simple swaps be fine?
Let's say a Near to Stable coin swap. At a hard coded Near <> USD price.
We could deploy stable coin contract and an LP as a part of the on_start() and then do swaps as the task.