refactor: RepresentativePowers to StakedTokens

[insumity]

Description

This is a minor-refactor PR and hence no issue is created for it.

Based on @p-offtermatt comment:

Seems ok to me. Could rename it to something like StakedTokens instead of RepresentativePowers (looking at the code, I think that's what this actually is, right?)

We rename RepresentativePowers to StakedTokens. We can see that StakedTokens is a better name if we look at what getRepresentativePower is computing, which is just the number of tokens:

func (tr TestConfig) getRepresentativePower(chain ChainID, validator ValidatorID) uint {
	//#nosec G204 -- Bypass linter warning for spawning subprocess with cmd arguments.
	bz, err := exec.Command("docker", "exec", tr.containerConfig.InstanceName, tr.chainConfigs[chain].BinaryName,

		"query", "staking", "validator",
		tr.validatorConfigs[validator].ValoperAddress,
		`--node`, tr.getQueryNode(chain),
		`-o`, `json`,
	).CombinedOutput()
	if err != nil {
		log.Fatal(err, "\n", string(bz))
	}
	amount := gjson.Get(string(bz), `tokens`)
	return uint(amount.Uint())
}

[p-offtermatt]

LGTM, thanks for the refactor! 🥇 just a nit, the prefix for the pr should probably just be refactor
https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json
not a big deal but this ensures that this is e.g. easily evaluated via machine