Fix positioning of Copy icons beside text

Summary

Copy icons that are beside text are inaccurately and inconsistently positioned. Several examples below. Considering setting standard spacing between the copy icon, the text it belongs to and adjacent content/controls. Also consider using an icon font for icons that need to be aligned to text (vs. graphics).

Screenshots

Not vertically aligned with text:

Not vertically aligned (issue sidebar):

Not vertically aligned or close enough to text it belongs to (repository file header):