Apache HTTP Client connection metrics

[j0hnc0yne]

Please describe the feature request.

The Apache HTTP Client metrics do not include the timings and count for when new connections are created. Reactor Netty has this as reactor.netty.http.client.connect.time / reactor.netty.http.client.tls.handshake.time. It would be useful to create a Timer metric that calculated the time it took to form a new connection for Apache HttpClient

Rationale

These metrics are useful to see both how often new connections are created as well as how long those take. Using that information can provide better insight into configuring the connection pool.

Additional context

As an example, the Timer could be wrapped around the PoolingHttpClientConnectionManager.connect method to track this metric