Add a keys delete command to remove keys from Hermes configuration

[andynog]

Crate

Hermes should provide a command to remove keys from its configuration. This might help with key maintenance and also to remove incompatible keys.

Summary

As a user/operator I want to have a command to remove a previously added keys for a chain removed from Hermes keys store (`~/.hermes/keys)

Problem Definition

Currently we only support updating keys adding or restoring them again. But there might be cases where a key needs to be removed (e.g. incompatible key)

Proposal

We should implement a command e.g. keys delete [chain-id] -n [key-name]

We could also implement a keys delete --all to clean the whole key store if it makes sense.

Acceptance Criteria

Keys are removed using the Hermes command

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[hu55a1n1]

Should we name the command delete instead of clean? Just to stay consistent with gaiad?