[Rosetta] Refactor testnet integration test script

[illia-malachyn]

How to test:

• cd integration
• python3 testnet_integration_test.py --init
• follow script instructions

[illia-malachyn]

I refactored only testnet_integration_test.py. There's also integration_test.py for testing against a local net and previewnet_integration_test.py is coming soon from Uliana's PR. They're pretty much similar, so as soon as her test is committed, I'll update both of them to make use of a new structure and functions to avoid code duplication

[illia-malachyn]

I notice that the tests' transactions fail at some point on testnet. There's a screenshot from Flow Diver. It is not related to refactoring, rather it is related to the Crescendo upgrade.

@peterargue Do you know what the potential reason is?

[peterargue]

As mentioned in standup, that error is most likely caused by a new feature on devnet that causes tx to fail that have not been upgraded to Cadence 1.0. I should be shut off now, so you can try again.

[illia-malachyn]

Closing in favor of #65