Try to get away with using only go/*, not golang.org/x/tools/go/packages

The code for loading the user's package uses golang.org/x/tools/go/packages. We redundantly load doc strings with go/parser. Maybe we can get away with just one or the other, not both.

Start at the code that loads the user's package with golang.org/x/tools/go/packages, then inspect where go/parser is used to load documentation strings. Determine whether either loader can provide everything required and verify the result with the existing project checks. Done means the redundant package-loading approach is removed without losing needed package or documentation information.

Written by the indexing model from the issue text.