Document usage of _FunctionsSkipCleanOutput and FunctionsPreservedDependencies

`_FunctionsSkipCleanOutput` and `FunctionsPreservedDependencies` do not have full coverage in official documentation. These should be covered in https://learn.microsoft.com/en-us/azure/azure-functions/functions-dotnet-class-library

This is a tracking item for this repo in support of other work items here. An item has also been filed in an internal docs system as part of the standard process there.

Start with the Azure Functions .NET class library documentation page linked in the issue and review how configuration properties are described. Document _FunctionsSkipCleanOutput and FunctionsPreservedDependencies there; done means both settings have complete official documentation and their coverage is consistent with nearby entries.

Written by the indexing model from the issue text.