Created Issue: [2.3] includereferencedprojects -symbols doesn't add sources for referenced project [3125]

1. classlibrary 1 references classlibrary2
2. nuget pack -includereferencedprojects - sybols

Actual:
the generated package contains pdb for both the projects but contains sources for classlibrary1 only

Expected:
to have sources of all referenced project (it might be a perf overkill for a huge solution with multiple references)