Add new integration tests for RandomAPI

[has5aan]

Description

Following modules are dependent on RandomAPI and make a good candidate for integration tests.

Modules dependent on RandomAPI

• DPoSModule

DPoSModule

• DPoSModule.afterTransactionsExecute consumes RandomAPI.getRandomBytes

Which version(s) does this affect? (Environment, OS, etc...)

Lisk SDK development branch.

[has5aan]

The test improvement suggested by the issue for PosModule consuming RandomMethod would require implementation of integration tests for the each PosModule which doesn't serve practically effective improvements based on the recent improvements activity for unit tests around each module.