[#702] Implement key revealing via RPC

Description

In Staker DAO we need key revealing made solely via RPC.

This MR implements it.

Along the way, I had to

• Add a PreviouslyRevealedKey error to RPC
• Refactor types with operation input. Previously we carried Either OriginationData TransferData, but now Either is not enough.

Related issue(s)

Resolves #702 (closed)

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