Go: Change provenance for MaD models that use package grouping

[owen-mc]

For example, the models for Revel use this package grouping:

extensions:
  - addsTo:
      pack: codeql/go-all
      extensible: packageGrouping
    data:
      - ["revel", "github.com/revel/revel"]
      - ["revel", "github.com/robfig/revel"]

With this PR, tests that use model pretty-printing will have this line when printing models

| 1 | Source: group:revel; Controller; true; Params; ; ; ; remote; manual |

instead of these lines

| 1 | Source: github.com/revel/revel; Controller; true; Params; ; ; ; remote; manual |
| 1 | Source: github.com/robfig/revel; Controller; true; Params; ; ; ; remote; manual |