No possibility to record connectTime with backend listener

**piotr.mirek** ([Bug 66262](https://bz.apache.org/bugzilla//show_bug.cgi?id=66262&redirect=false)):
Currently backend listener provided with core JMeter binaries not allows to get information about connect time, which is crucial when having issues on connection. Please add this functionality to current backend listener implementation.
Something similar is provided but in much bigger scope here:
https://github.com/adrianmo/jmeter-backend-azure

It would be best if user could actually pick what should be processed by backend listener for test specific needs (e.g. list all fields to process, separated by comma, with defaults already pre-filled, or some other way)

Severity: normal
OS: All