bugfix for container port range

[singholt]

Summary

This PR makes 2 bug-fixes:

1. fix ports information logged in agent logs.
2. fix port search for case when 1 container requests multiple container port ranges.

Implementation details

1. We currently log ports information in agent logs here and here. With this project, we made the containerPort and containerPortRange pointer to int/string values. So the logger is now logging the addresses of variables, rather than the values themselves. We have 2 options to fix this:
   a) Encode the ports into JSON and then print it. example
   b) Change the references back to values. The reason why these were references in the first place is because we wanted to perform nil checks. Since we know that containerPort: 0 and containerPortRange: "" are not valid (validated on ECS side), we can stick to non-references.
   We're doing option (b) in this PR, since its simple and also avoids a lot of type conversions in unit tests.

2. Fixing concurrent host port search when a container requests multiple port mappings, each with a container port range. Currently, we lock the method where we do host port search. Once we identify host ports, we send it to docker which then maps it. A case where the same container requests multiple container port ranges, would get the same host ports picked because we do the search (for both ranges) before sending a create-container call to docker. This PR fixes it by tracking which host port was last picked and locking read/updates to this tracker. Note that the method to get host ports is also concurrent-safe to prevent two task-level go routines get ports at the same time.

Testing

1. Modified existing unit tests based on the refactor.
2. Tested the changes manually by building an AMI with these changes and running 50 tasks at the same time, each with a container requesting multiple container port ranges.

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.

[YashdalfTheGray]

Reapproving after testing fix rebase.

[amogh09]

Approving the rebase.

[amogh09]

Approved. As discussed offline, the loop-back may result in Agent finding overlapping ranges for a single container in some cases (which would result in container failing to start) but that's a risk we are willing to take for the potential benefit of finding contiguous port ranges.