Consider blocking TaskLoggingHelper use after its task ends

[rainersigwald]

see #4792 (comment) and the rest of that thread

If you hold onto a TaskLoggingHelper object (perhaps in a static field) past the lifetime of the Task that created it, it will throw when it is used.

We could instead dispose of it and provide a nicer error at time of use.

[KirillOsenkov]

@jeromelaban is reporting he's seeing what I think is the same issue: an orphaned LoggingService: https://source.dot.net/#Microsoft.Build/BackEnd/Components/Logging/LoggingService.cs,ee48c26bd0246ed6,references