Port PR from PBS-Go: Metrics: Record HTTP connections wanted and obtained

[cross-repo-issue-creation]

A PR was merged over on PBS-Go

• Metrics: Record HTTP connections wanted and obtained prebid-server#4518
• timestamp: 2025-09-04T19:11:50Z

[AntoxaAntoxic]

Vertx Framework that is used in PBS Java already supports all necessary metrics. So it's nothing to do on the PBS Java side.