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

[KaloyanTanev]

🎯 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: Add User-Agent HTTP header for validator client requests sigp/lighthouse#7963
  PR: add user-agent header to all http clients sigp/lighthouse#8786
• Teku
  Issue: Set User-Agent header for any outbound http requests Consensys/teku#9602
  PR: Add User-Agent header with Teku version on VC requests Consensys/teku#9935
• Nimbus
  Issue: Add Nimbus version to all requests status-im/nimbus-eth2#7427
  PR:
• Prysm
  Issue: Set User-Agent header for any outbound http requests OffchainLabs/prysm#15435
  PR: adding user agent validator beacon client OffchainLabs/prysm#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.

[pinebit]

I think the proper way to solve this is to ask clients to report proper User-Agent. Hope that's doable.
I submitted a request with Teku and asked to change the behavior: Consensys/teku#9602

[pinebit]

Request for Prysm: OffchainLabs/prysm#15435

[KaloyanTanev]

Should be done on client teams side.

[KaloyanTanev]

Prysm is fixed ✅

[KaloyanTanev]

I've opened an issue for Nimbus as well: status-im/nimbus-eth2#7427

[KaloyanTanev]

Opened for Lighthouse: sigp/lighthouse#7963