feature: container port range mapping (merging into dev)

[singholt]

Summary

This PR merges the feature/container-port-range branch into dev.

Implementation details

All changes have been reviewed in individual PRs targeting the feature branch. This is just a merge back to dev for feature release.

Here's a feature summary:

• The existing singular port mapping customer experience remains the same. There are no new changes introduced to it, by this port range mapping feature.
• We're adding the ability to process container port range(s) belonging to containers (in a task payload). The corresponding host port range will be dynamically mapped.
• Dynamic port mapping is only applicable to default/bridge/nat network modes.
• The agent advertises a new capability to ensure only agent capable of handling the port range(s) gets the task payload.
• We've updated the ECS model and API contract so that the agent is able to recognize ranges and communicate with ECS about the same.
• For each range, the agent attempts to find a contiguous host port range for dynamic assignment. It does so by checking the default ephemeral range. In case there is no contiguous set of ports available, docker does assignment.
• The agent sends network bindings information to ECS as part of the submit task/container state change payload.

Testing

New tests cover the changes: yes

Description for the changelog

Feature: container port range mapping

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.