Add support for using repositories from GitHub Connection as the source for steps in Process and Project Templates

[N-lson]

The enhancement

The Need

GitHub Connections were added to the Platform Hub as part of #9930. However, only support for using them to configure the Platform Hub-wide Version Control Settings was added. These connections should also be usable in steps in templates.

Solution

Allow selecting GitHub Connections configured in the Platform Hub in steps in Process and Project Templates.