Expand s_whitespace to check for newlines in .cpp files

Summary
s_all's run of s_whitespace does not check for newlines in .cpp files. Expand the check so that .cpp files get checked.

This will also expands s_whitespace to check for white spaces and extra lines in the .cpp files also. 

Acceptance Criteria (Definition of Done)
Test the changes are working, and newlines are added to .cpp files that are missing them.