Investigate ibc-go-test behaviour with inactive validators

[p-offtermatt]

Problem

Reported by @sainoe

The ibc-go test suite uses the staking module to get historical information here:
https://github.com/cosmos/ibc-go/blob/7e01c9149149b9d4b1d871e58eb88a22f15bdb3c/testing/chain.go#L403

This might become inaccurate after the inactive validators feature. A short investigation is needed to determine how/whether we need to adjust.

Our understanding at this point is that this does not have an impact on the behaviour in production; it should just affect tests.

Closing criteria

It is clear whether and where changes need to be made to ensure the behaviour with inactive validators is accurate in ibc-go tests.