Require fee_recipient in commands

[corverroos]

Problem to be solved

Fee_recipient is optional in all commands: create dkg, create cluster, dkg.

This results in empty fee_recipient in charon run that results in warning logs:

Proposing block with unexpected fee recipient address {"expected": "", "actual": "0x0000000000000000000000000000000000000000", "duty": "4736088/proposer"}

Proposed solution

Either make it non-optional, so check it isn't empty.

Or make it default to withdrawal address, but this is implicit log and require documentation and warnings and stuff which isn't great.

[OisinKyne]

Yeah lets not make a default nor should it be optional.

However if --definition-file is passed that overrides (all?) other flags, so its not needed then, but the definition-file should also assert that a fee_recipient is set.

Open Q: How might this flag work if we tried to make it compatible with multiple withdrawal addresses and multiple fee recipients? 🤔 CC @dB2510 (out of scope of this ticket though)

[dB2510]

This is already done as part of #1756