Port new triple slash docs for .NET 7 Alpha [Nov - Dec '21]

[carlossanlop]

As mentioned before, I plan on submitting automatic porting PRs every month to avoid debt right before shipping.

There wasn't any docs churn in the last month in runtime. Fortunately, most of the missing docs were taken care of in my PR from a month ago: #7424

MSBuild - @ghogen one tiny returns value was ported.
System.Workflow - @dotnet/docs are listed as owners of System.Workflow in the CODEOWNERS file.

cc @jeffhandley

[gewarren]

LGTM

[opbld30]

Docs Build status updates of commit de74fd9:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/Microsoft.Build.Tasks/Copy.xml	✅Succeeded	View
xml/System.Workflow.ComponentModel.Compiler/CompileWorkflowTask.xml	✅Succeeded	View

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