Currently all the documentation files that we include in our packages come from the intellisense package we consume from the docs team. However, some projects have already ported their documentation to triple slash, so we should be packaging the resulted xml file from the roslyn compilation on those projects.
In order to support that we should introduce a property, maybe IncludeDocumentationFromSource, and have the infra choose the generated file rather than the downloaded one: #54250 (comment)
cc: @carlossanlop @ViktorHofer @Anipik @ericstj