cmVSGenerator: Add support for two-part toolset versions for Visual Studio

Enables the Global Visual Studio Versioned Generator to use two-part toolset versions,
if only one toolset has that version number. For example, (14.32 is specified when
14.32.32142 and 14.32.23242 are installed). This change also add a unique return code
and message if a two-part version is used when multiple matching versions are present.

Fixes: #23933