…when-revision-is-included

Fix `gvfs clone` version check when revision is included in the version string

As reported by Tyrie Vella, `gvfs clone` would fail with https://github.com/microsoft/VFSForGit/releases/tag/v1.0.25260.1 when the repository to clone specifies a minimal VFSforGit version in its `gvfs/config` endpoint. The reason is that with the version bump from .NET SDK v3 to v9, the version string included in the assembly now contains the suffix `+<commit-SHA>`, which cannot be parsed by `System.Version`:

```
Cannot clone @ C:\path: System.FormatException: Input string was not in a correct format.
   at System.Version.VersionResult.SetFailure(ParseFailureKind failure, String argument)
   at System.Version.TryParseComponent(String component, String componentName, VersionResult& result, Int32& parsedComponent)
   at System.Version.TryParseVersion(String version, VersionResult& result)
   at System.Version.Parse(String input)
   at System.Version..ctor(String version)
   at GVFS.CommandLine.GVFSVerb.TryValidateGVFSVersion(GVFSEnlistment enlistment, ITracer tracer, ServerGVFSConfig config, String& errorMessage, Boolean& errorIsFatal)
   at GVFS.CommandLine.GVFSVerb.ValidateClientVersions(ITracer tracer, GVFSEnlistment enlistment, ServerGVFSConfig gvfsConfig, Boolean showWarnings)
   at GVFS.CommandLine.CloneVerb.Execute()
```

Matthew Cheetham provided a quick work-around in #1870 to opt out of the new behavior and report the version _without_ that suffix again; Here is a PR that prepares the code to handle such versions gracefully, to open up the door to opt back in to the new behavior (and let `gvfs version` report an even more informative output than right now).