[NCC-E008263-AW3] Insufficient Participant Commitment List Checks

[conradoplg]

sign() does not properly validate the signing_package.signing_commitments. See report for more details.

Fix it, so it checks:

• If the participant's identifier and commitment is included (done in Add validation for missing identifier in signing package #452)
• If there aren't any repeated commitments
• Check consistency with min_signers/max_signers? We'll need to think a bit about this since those aren't readily available. It may be a good idea to store min_signers in the KeyPackage, but max_signers might not possible (since it's possible to issue new shares).

[conradoplg]

We decided that it's not needed to check for repeated commitments, since that would just cause the signature generation to fail.