shed: set control address: add dump bytes option

[arajasek]

Related Issues

Helps (but does NOT close) #9563

Proposed Changes

Right now, the Filecoin protocol only allows the owner address to set control addresses. Changing this requires a FIP & network upgrade.

Since some owner keys are maintained by folks that don't run Lotus nodes, it might be useful to share the raw bytes of such messages with them, for them to sign offline, and return to someone capable of pushing the signed message to the network. This is imperfect for a few reasons:

• the entity that has the owner key should confirm the bytes are in fact the message they intend to send
• the gas estimation is performed at the time this command is run, and may be poor estimation for the time when the message is sent out
• the worker really should be able to do this.

Additional Info

Checklist

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