feat(ecs/services): cloudwatch metrics and dashboard widgets

[mskrajnowski]

• enabled ECS cluster container insights
• Added ecs/services/web metrics:
  • requests count
  • response count by status (2xx, 3xx, 4xx, 5xx)
  • response percentage by status
  • ALB connection errors
  • ALB connection error percentage
  • response times (average, 50/90/95/99th percentiles, maximum)
  • task counts (desired, pending, running, healthy)
  • cpu/memory reservation
  • cpu/memory utilization (min, average, max)
• Added ecs/services/web dashboard widgets
  • responses by status
  • response status percentages
  • response times
  • scaling
  • cpu utilization
  • memory utilization
• Added ecs/services/worker metrics:
  • task counts (desired, pending, running)
  • cpu/memory reservation
  • cpu/memory utilization (min, average, max)
• Added ecs/services/worker dashboard widgets:
  • scaling
  • cpu utilization
  • memory utilization
• Added a simple locustfile.py to generate some traffic for testing

Example dashboard

Related to #43