perf: replace inject("+") with sum and use filter_map in utils

- Replace `results.values.inject("+")` with `results.values.sum` in
  analytics.rb (two call sites)
- Replace chained `.reject(&:build?).reject(&:test?).map(&:to_formula)`
  with `.filter_map { |d| d.to_formula if !d.build? && !d.test? }` in
  topological_hash.rb