v4 task server setup

[cyastella]

Summary

Create v4 endpoint for the task/container with metadata/stats and set up task server.

Implementation details

Add v4 endpoint to fetch the info about the containerMetadata, taskMetadata, containerStats and taskStats with the specific paths. Test different network mode of the tasks like awsvpc, non-awsvpc mode and check the network info works as we expected.

Example awsvpc containerMetadata network info looks like:

"NetworkMode": "awsvpc",
"IPv4Addresses": ["172.31.47.69"],
"AttachmentIndex": 0,
"IPv4SubnetCIDRBlock": "172.31.32.0/20",
"MACAddress": "06:96:9a:ce:a6:ce",
"PrivateDNSName": "ip-172-31-47-69.us-west-2.compute.internal",
"SubnetGatewayIpv4Address": "172.31.32.1/20"

Example bridge containerMetadata network info looks like:

"NetworkMode": "bridge",
"IPv4Addresses": ["172.17.0.2"],
"AttachmentIndex": 0,
"IPv4SubnetCIDRBlock": "",
"MACAddress": "",
"SubnetGatewayIpv4Address": ""

Testing

Add unit tests for the task server set up to test v4 endpoint.

New tests cover the changes: yes

Description for the changelog

Licensing

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