chore(*): remove unnecessary transitive imports (#2496)
This removes all imports which have already been imported by other imports.
Overall, this is slightly over a third of the total import lines. This should have no effect whatsoever on compilation, but should make `leanproject import-graph` somewhat... leaner!
Co-authored-by: Scott Morrison <scott.morrison@gmail.com>
Co-authored-by: Keeley Hoek <keeley@hoek.io>
