Improve test suite testutil/keeper by adding utility methods for state initialization

[lumtis]

Many of our tests depend on some state initialization, like creating a chain, a campaign, a coordinator, etc...

Those initializations are performed manually using keeper exposed methods

We should provide in testutil/keeper package utility methods to perform repetitive initialization

We have already for example a method Mint that perform all the necessary step from the bank keeper to mint and transfer funds to a specific address.

Example of methods:

CreateChain
CreateChainWithRewards
CreateMainnet

• Investigate and identify methods to implement
• Implement methods or create tasks accordingly depending on the complexity