Partial Set Security: review the standalone to consumer changeover

[sainoe]

The standalone to consumer changeover process was built under some assumptions that do not hold with PSS, and therefore needs to be reviewed.

[insumity]

Looked into the changeover logic and did not find anything that could be problematic in relations to PSS and standalone to consumer changeover logic. PSS did not change anything on the consumer-module side. Therefore, PSS could not have an impact on the changeover logic (e.g., ChangeOverToConsumer) that exists on the consumer module. The consumer chain would use the initial validator updates created from MakeConsumerGenesis and whether the consumer chain is standalone or not is irrelevant.
Lastly, I modified (locally) the E2E changeover test using TopN = 0 instead of TopN = 100 in the SubmitConsumerAdditionProposalAction, as well as passing a ValidatorSetCap to 2 and everything worked as expected.