[docker] New docker check

This is a new version of the docker check, it's called docker_daemon (name can be changed).
The previous check "docker" is now deprecated and won't receive further support.

In terms of features, this adds:
- Support for TLS connections to the daemon
- New metrics:
    - Network metrics
    - Memory limits
    - Container size (rootfs)
    - Image size
- Support for labels (convert them into tags). Off by default, uses a list of labels that should be converted.
- Support for ECS tags: task name and task version

Backward incompatible changes:

    - docker.disk.size metric is renamed to docker.container.size_rw
    - Old optional metrics: https://github.com/DataDog/dd-agent/blob/5.4.x/checks.d/docker.py#L29-L38 Are not collected anymore
    - Old old tags are not supported anymore (e.g. `name` instead of container_name)

fix: DataDog#1299 DataDog#1648 DataDog#1739 DataDog#1742 DataDog#1896

conf.d/docker.yaml.example

@@ -27,11 +27,6 @@ instances:
     # Example:
     # tags: ["extra_tag", "env:example"]
 
-    # If the agent is running in an Amazon ECS task, tags container metrics with the ECS task name and version.
-    # Default: true
-    #
-    # ecs_tags: false
-
     # Exclude containers based on their tags
     # An excluded container will ne longer report performance metrics or events. However,
     # we still count the number of running and stopped of all containers.
@@ -72,6 +67,6 @@ instances:
     # collect_all_metrics: false
 
     # Collect images stats
-    # Number of available active images and intermediate images as gauges. Default: true.
+    # Number of available active images and intermediate images as gauges. Default: false.
     #
     collect_images_stats: false