attestation: add name to Validator as unique identifier

[jmxnzo]

This PR is a follow-up on #1027 and aims to enhance the logging of the different validation processes on the coordinator to reach better readability of the logs.

• Name was introduced as unique identifier in Validator struct and mapping to manifest.json, following the naming convention:
  <attestation>-<reference-values-index>[-<product>]
  The index corresponds to the position of the reference value separated by attestation type in manifest.json.
• It was ensured that if all validators fail, the joined error message is printed and the formatting was reworked for readability.
• Single validation failures are printed on DEBUG only instead of ERROR level using the validator name and nonce.

[jmxnzo]

Wait for merge of #1082