OpenBrush follow-up 2 milestone 7 modification

[xgreenx]

Many developers are asking for the feature to test cross-contract calls in unit tests because it is hard to mock it each time and makes the testing much harder, forcing people to write integration tests with Redspot, Swanky, and Typechain-Polkadot.

We want to prioritize this task and deliver the trait refactoring in ink! later(Initially, we plan to implement an advanced testing framework in milestone eight it is why we can swap those tasks). Because it is a hot topic and after discussion in the issue and element channel, it is clear how it should be implemented=)

The scope of work is the same and also related to the ink! repository. Because it requires modification of the off-chain environment.

Grant level

• Level 1: Up to $10,000, 2 approvals
• Level 2: Up to $30,000, 3 approvals
• Level 3: Unlimited, 5 approvals (for >$100k: Web3 Foundation Council approval)

#921

[CLAassistant]

All committers have signed the CLA.

[alxs]

Sounds good!