Unable to fetch validator alias because it's not part of validator metadata

[McDaan]

As I have been following the development of a Namada explorer, I evidently saw the need to fetch the validator aliases, which it's not possible currently. It would be really needed for explorers, wallet interfaces, consensus dashboards, etc., so as to show full validator information (whether it's pre or post-genesis).

Thus, what I propose in order to address this problem is to add a new validator metadata field to store the validator alias. It would definitely improve the UX in the mentioned situations.