Add and apply Style/InvertibleUnlessCondition rule

This rule was added in rubocop 1.44.0. It's useful to avoid accidental
`unless !condition` clauses.

Note we aren't replacing `unless zero?` with `if nonzero?` because we
never use `nonzero?`; using it sounds like `if !zero?`.

Replacing `unless any?` with `if none?` is only consistent if we also replace
`unless present?` with `if blank?`, so we're also adding this case. For
consistency, we're also replacing `unless blank?` with `if present?`.

We're also simplifying code dealing with `> 0` conditions in order to
make the code (hopefully) easier to understand.

Also for consistency, we're enabling the `Style/InverseMethods` rule,
which follows a similar idea.

app/controllers/admin/api/stats_controller.rb

@@ -1,9 +1,9 @@
 class Admin::Api::StatsController < Admin::Api::BaseController
   def show
-    unless params[:event].present? ||
-           params[:visits].present? ||
-           params[:budget_investments].present? ||
-           params[:user_supported_budgets].present?
+    if params[:event].blank? &&
+       params[:visits].blank? &&
+       params[:budget_investments].blank? &&
+       params[:user_supported_budgets].blank?
       return render json: {}, status: :bad_request
     end