ZedRun simulation tests

[mikedotexe]

ZedRun is looking to make sure they have tests for the cross-contract calls they have, as that's a very important part of their app. This means providing them with a reasonable example or helping them understand how to implement this.

Currently the two places where simulation tests are being used (that I'm aware of) are both in the core-contracts:

• https://github.com/near/core-contracts/blob/master/lockup/tests
• https://github.com/near/core-contracts/tree/master/staking-pool/tests

These implementations are fairly advanced, and we need to be able to translate this process for new partners. Acceptance Criteria:

• ZedRun is able to run their own simulation tests
• Bonus points: there is a simplified version of simulation tests that is consumable for future partners

[mikedotexe]

Made progress here: https://github.com/near-examples/simulation-testing Really, really needs a good README. I will be doing that, but it's almost the end of the day. NEARly there

[mikedotexe]

Got a great start on the README, hoping to be done with that by EOD Wednesday