[Feature]: Only consider one pre-sign request per bitcoin block

[djordon]

Feature - Only consider one pre-sign request per bitcoin block

1. Description

The signers should only consider one pre-sign request per bitcoin block. This is to protect the signers from doing unnecessary work. If they get two, it's probably an error or something, and can be safely ignored.

2. Technical Details:

The signers should keep track of the pre-sign requests from the coordinator for each bitcoin block and ignore the request if you get more than one.

2.1 Acceptance Criteria:

• The signers consider at more one pre-sign request per bitcoin block

3. Related Issues and Pull Requests (optional):