Test-RemoteConnection should actually test a call to remoting

[michaellwest]

The current behavior with Test-RemotingConnection tries to hit the keepalive page in Sitecore, but does not actually verify a call through the SPE Remoting. Proposing a change where the command returns some minimal details needed to test that it works.

[michaellwest]

What makes this a breaking change is that the results which comes back is a different object. Previously you would see System.Net.HttpWebResponse object or System.Net.WebException

New example output:

SPEVersion  SitecoreVersion CurrentTime         
----------  --------------- -----------         
6.2.0.27129 9.3.0.3498      10/3/2020 6:14:26 AM