`core_validatorapi_vc_user_agent` does not report end user readable VC types and versions

🎯 Problem to be solved

The metric that we push to prometheus core_validatorapi_vc_user_agent does not always send readable VC type/version. For Lighthouse it doesn't even send one.

i.e.:
okhttp/4.12.0 is for Teku. While we know okhttp is a Java HTTP library and we know only Teku uses Java from our stack, it's not intuitive for users.
Similar to Go-http-client/1.1 and Prysm.

🛠️ Proposed solution

Ask VCs to include the correct header.

• Lodestar
• Lighthouse
  Issue: https://github.com/sigp/lighthouse/issues/7963
  PR: https://github.com/sigp/lighthouse/pull/8786
• Teku
  Issue: https://github.com/Consensys/teku/issues/9602
  PR: https://github.com/Consensys/teku/pull/9935
• Nimbus
  Issue: https://github.com/status-im/nimbus-eth2/issues/7427
  PR: https://github.com/status-im/nimbus-eth2/pull/8627
• Prysm
  Issue: https://github.com/OffchainLabs/prysm/issues/15435
  PR: https://github.com/OffchainLabs/prysm/pull/15574
• Vouch

🧪 Tests

Check for all VCs (including the newly supported - Vouch) if they are properly displayed in the Validator Client Version in Grafana. Easy to test using Kurtosis.