[Fix]: Re-enable bootstrapping the signer set

[djordon]

Feature - Re-enable bootstrapping the signer set

1. Description

We accidentally removed the ability of bootstrapping the sBTC signers from scratch. This can happen when starting off in a fresh network without any of the smart contracts being deployed. In this case, the signers will not sign for the smart contracts because they have no verified shares, and no signer set info in the registry because the registry has not been deployed!

2. Technical Details:

So allow for signing a smart contract deployment in the case where the registry has not been deployed and where we do not have verified shares.

2.1 Acceptance Criteria:

• The signers can bootstrap themselves

3. Related Issues and Pull Requests (optional):