Finch telemetry

Added start_pool_metrics?: true to application.ex

%{
  :default => [size: 12000, protocols: [:http1], start_pool_metrics?: true]
}

# Finch metrics
Metrics.distribution(
  "finch.request.duration.milliseconds",
  event_name: [:finch, :request, :stop],
  unit: {:native, :millisecond},
  tags: [:name],
  measurement: :duration,
  reporter_options: [
    buckets: [50, 100, 200, 400, 800, 1600]
  ]
),
Metrics.counter(
  "finch.request.error.count",
  event_name: [:finch, :request, :exception],
  tags: [:name, :kind]
)