Abstract tests in /modules to run with Bee class as well

[vojtechsimetka]

Tension:
Right now we are unnecessarily replicating tests in the Bee class that are already in the individual modules

Proposed solution:
Abstract the tests so that they can be run on both the Bee class and the module. Good example how this can be done is https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/test/token/ERC777/ERC777.test.js#L43-L59

See discussion #15 (comment)

[vojtechsimetka]

On the testing meeting on March 7th 2021 we decided we do not need to run the tests against both Bee class and individual modules. We will only run the tests for the functionality against the modules themselves (just as we do right now) and then test the bee class only for the assertion of params #248 .