Consolidate on a single clone experience in VS

[acangialosi]

VS has a single clone API with two other clone user experiences which we are working on consolidating into one. We would like to avoid introducing a third workflow for clone with its own behaviors and discoverability. Top level entry points for getting to VS' shared clone experience exist in the start window, File Menu and will surface with more shortcuts directing you to that experience. This will ensure we have a consistent behavior for all git hosted content and all hosts benefit from improvements in the future.