Created by: linzhp
For most Go IDE/tools to work, every imported package has to be in some proper directories under GOPATH. However, Go code generated during a Buck build is not. This PR copies them to the vendor directory as part of "buck project --ide=intellij", although this change not only makes the IntelliJ/GoLand work, but also enable other IDEs and static check tools work with Go projects built with Buck.
In order for "buck project" command to identify Go targets and IjProjectCommandHelper to use Go related classes, I moved the Go module from features to core.
@styurin @kageiit Please review