Add generic deb packaging

[sparrc]

Summary

Add generic deb packaging (one that is not specific to platform).

Implementation details

Some changes from the ubuntu-trusty packaging:

• changed maintainer from skarp@amazon to ecs-agent-dev@amazon
• changed deb changelog distribution from "trusty" to "stable" and added --lintian-opts --suppress-tags bad-distribution-in-changes-file to suppress "bad distribution" linter error. This is because "stable" is not a valid distribution name for Ubuntu.
• added a list of possible docker engine sources instead of only docker-engine: docker-ce (>= 17.12.0) | docker-engine (>= 1.6.0) | docker-ee | docker.io
• added a post-install script to enable the ecs service
• added override_dh_auto_install rule to add the bundled agent container tarball to the cache directory
• added ecs.service file, removed ecs.conf (only supporting systemd for now)
• remove DEB_SIGN option as it is not used
• add arm64 as a valid architecture to the control file
• download and cache the relevant agent tarball version for the tagged version of init. Previously we were not caching this so ecs would have just downloaded the latest version on startup.
• install systemd service file via dh_installsystemd --no-start --no-enable --name=ecs

Testing

Built the deb and tested it on:

• [x] ubuntu 20.04
• [x] ubuntu 18.04
• [x] debian 10
• [x] debian 9
• [x] ubuntu 20.04 ARM
• [x] ubuntu 18.04 ARM
• [x] debian 10 ARM
• [x] debian 9 ARM

Verified that the service runs fine on these platforms.

Description for the changelog

N/A

Licensing

This contribution is under the terms of the Apache 2.0 License:

[nmeyerhans]

Omit the docker dependency. This is mainly because we have less control over docker outside of AL. it can come from "docker-ce", "docker" or "docker-ee", or even not from deb. so i omit this dependency in packaging;

The debian packaging format allows optional dependencies. You should specify a Docker dependency using something like: Depends: docker-ce | docker-ee | docker.io | docker

This obviously won't cover the case where it's not installed via a package, but for people going that route, they will have other issues, and other ways of satisfying the dependency.

We should not be leaving critical dependencies unspecified