Allow to run `collect` blocks in every process of multi-process app

[ollym]

We managed to make this work by adding the following to puma.rb

on_worker_boot(:connection_pool_timer) do |index, data|
  ActiveSupport.on_load(:active_record) do
    data[:connection_pool_timer] = Concurrent::TimerTask.new(execution_interval: 2) do
      ActiveRecord::Base.connection_handler.all_connection_pools.each do |connection_pool|
        tags = { index: index, name: connection_pool.db_config.name }
        connection_pool.stat.each do |name, value|
          Yabeda.activerecord.send(:"connection_pool_#{name}").set(tags, value)
        end
      end
    end.tap(&:execute)
  end
end

on_worker_shutdown(:connection_pool_timer) do |index, data|
  data[:connection_pool_timer]&.shutdown
end

But what do you think about supporting this out the box?