feat(client/v2): add key lookup interface

[julienrbrt]

Description

ref: #14744

#17306 should be merged before.

Add simple keyring interface (to be expended in follow-ups) and wiring it in address flags handlers.
It allows using a key name instead of any addresses in queries/tx.

I'll wire this in the SDK in a follow-up.

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[github-actions]

@julienrbrt your pull request is missing a changelog!

[julienrbrt]

@julienrbrt your pull request is missing a changelog!

client/v2 does not have any changelog.