Documentation for pipeline configuration

The various pipelines that exist for the .NET Docker builds have a lot of parameters that are not described. They rely on tribal/historical knowledge held by the repo maintainers. This makes it difficult for new engineers as well as experienced maintainers that have simply forgotten about or weren't aware of certain parameters. There should be better documentation for what these parameters are, including descriptions of additional parameters that can be added to a pipeline to control behavior (such as `noCache`).