XTC/XLT - Custom Machine Usage

[rschwietzke]

Custom machines are an option for XTC. We have not properly documented that currently (when this is enabled for an org). This includes the hint to take care of the agent password and version. Also, the format required for the machine list (IP:Port, IP, hostname:IP, hostname and never a protocol) is important.

In addition, one might point to the machine setup documentation to clarify how the password get into the either AWS/GCP machine or how one sets that up when the machine is a custom setup (not using XC images and AWS/GCP CLI tooling).