VS: Revert "Add missing label in C# project-build events"
Revert !6485 (merged). The change broke cases using
multiple successful custom commands. Revert it pending further
investigation into the interaction of the generated script code with
Microsoft.Common.CurrentVersion.targets
, and whether this is needed
for all managed projects or just C# projects.
Also add a test covering the case that was broken.
Fixes: #22964 (closed)
Issue: #21440 (closed)
Backport: release