Update logic for how workload version is displayed

[dsplaisted]

The workload version can be displayed via dotnet workload version, and is also displayed in dotnet workload --info.

• If in a context with a workload set version specified in global.json, the version from global.json should be displayed. If that workload set version isn't currently installed, dotnet workload --version should still display it wiithout erroring.
• If a workload set is in use, its version should be displayed
• If not using a workload set, or if the update mode is set to workload sets but no workload set is installed, then display a version based on a hash of the workload manifest versions, which looks something like 8.0.300-manifests.ab95c30

Also, we should update dotnet workload --info to display the workload config settings (currently just the update mode).

FYI @baronfel @marcpopMSFT @Forgind