CCM fees are under-specified and the implementation is not defensive

[ishantiw]

Description

if the beforeCrossChainMessageForwarding function of the token module should only work with LSK, then add a check to ensure that messageFeeTokenID is always LSK. Create a function that, given a CCM, returns the messageFeeTokenID. This will reduce the ambiguity of using receivingChainID or sendingChainID, and ensure that all functions use the same.

• Add getMessageFeeTokenIDFromCCM method to Interoperability module

Acceptance Criteria

• Should pass all the unit tests

Additional Information

Relevant LIP PRs,

• Update beforeCrossChainMessageForwarding in LIP 0051 to check messageFeeTokenID lips#426
• Add getMessageFeeTokenIDFromCCM method to Interoperability module lips#437